Photoelectric sensor and forming method thereof

Abstract

The photoelectric sensor comprises a substrate, the substrate is provided with a light receiving surface and comprises a light sensing pixel area, the light sensing pixel area comprises a plurality of pixel unit areas which are distributed in a matrix mode, in the pixel unit areas, a plurality of first protrusions are formed on one side of the light receiving surface of the substrate, and a plurality of second protrusions are formed on the other side of the light receiving surface of the substrate; the transverse size and the longitudinal size of the first protrusion are both smaller than the wavelength of light. And the light transmitting layer covers the light receiving surface of the substrate and is filled between the adjacent first bulges. According to the invention, the reflection loss of light is reduced, the transmission of light on the light receiving surface is increased, the number of transmission photons is effectively increased, and the collection of light signals is increased, so that the photoelectric detection efficiency is improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular to a photoelectric sensor and a method for forming the same. Background Art

[0002] Photoelectric sensors are devices that convert light signals into electrical signals. Their working principle is based on the photoelectric effect, which refers to the phenomenon that when light shines on certain substances, the electrons of the substances absorb the energy of photons and produce corresponding electrical effects.

[0003] For example, CCD (Charge Coupled Device) image sensors and CMOS image sensors use the photoelectric conversion function to convert optical images into electrical signals and then output digital images. They are currently widely used in digital cameras and other electronic optical devices. ToF (Time of Flight) distance sensors project a modulated infrared light source onto an object, person or scene, and then the reflected light is captured by the ToF sensor, which measures the light intensity and phase difference received by each pixel to obtain a highly reliable depth image and a grayscale image of the entire scene. This technology can be used in various distance measurement scenarios such as autonomous driving, sweeping robots, VR (Virtual Reality) / AR (Augmented Reality) modeling, etc.

[0004] Photoelectric sensors all have a pixel area of ​​a certain area for receiving optical signals. The higher the optical transmittance of the pixel area, the better the optical sensitivity performance of the device.

[0005] However, the photosensitivity of currently formed photoelectric sensors needs to be improved. Summary of the invention

[0006] The problem solved by the embodiments of the present invention is to provide a photoelectric sensor and a method for forming the same, so as to improve the imaging quality.

[0007] To solve the above problems, an embodiment of the present invention provides a photoelectric sensor, including: a substrate, the substrate having a light receiving surface, and the substrate including a photosensitive pixel area, the photosensitive pixel area including a plurality of pixel unit areas distributed in a matrix, in which a plurality of first protrusions are formed on one side of the light receiving surface of the substrate, and the lateral and longitudinal dimensions of the first protrusions are both smaller than the wavelength of light; a light-transmitting layer, covering the light receiving surface of the substrate and filling between adjacent first protrusions.

[0008] Optionally, in the pixel unit region, a distance between adjacent first protrusions is smaller than a wavelength of light.

[0009] Optionally, in the pixel unit area, a plurality of first protrusions are distributed in an array.

[0010] Optionally, the shape of the first protrusion includes a cylinder, a truncated cone, a prism or a cuboid.

[0011] Optionally, the lateral dimension of the first protrusion gradually increases from the top to the bottom.

[0012] Optionally, a plurality of second protrusions are formed on the top of the light-transmitting layer, and the lateral and longitudinal dimensions of the second protrusions are both smaller than the wavelength of light.

[0013] Optionally, the interval between adjacent second protrusions is smaller than the wavelength of light.

[0014] Optionally, a plurality of second protrusions are distributed in an array.

[0015] Optionally, the second protrusion has a shape including a cylinder, a truncated cone, a prism or a cuboid.

[0016] Optionally, the lateral dimension of the second protrusion gradually increases from the top to the bottom.

[0017] Optionally, the photoelectric sensor further includes: a light isolation structure located in the substrate adjacent to the pixel unit area.

[0018] Optionally, the photoelectric sensor is a back-illuminated photoelectric sensor.

[0019] An embodiment of the present invention also provides a method for forming a photoelectric sensor, including: providing a substrate, the substrate having a light receiving surface, and the substrate including a photosensitive pixel area, the photosensitive pixel area including a plurality of pixel unit areas distributed in a matrix; patterning the substrate, in the pixel unit area, forming a plurality of first protrusions on one side of the light receiving surface of the substrate, the lateral size and the longitudinal size of the first protrusions are both smaller than the wavelength of light; forming a light-transmitting layer covering the light receiving surface of the substrate, the light-transmitting layer also filling between adjacent first protrusions.

[0020] Optionally, in the step of forming a plurality of first protrusions on one side of the light-receiving surface of the substrate, in the pixel unit region, a spacing between adjacent first protrusions is smaller than a wavelength of light.

[0021] Optionally, in the step of forming a plurality of first protrusions on one side of the light-receiving surface of the substrate, the lateral dimensions of the first protrusions gradually increase from the top to the bottom.

[0022] Optionally, a plurality of first protrusions are formed on one side of the light-receiving surface of the substrate by using a dry etching process.

[0023] Optionally, after forming a light-transmitting layer covering the light-receiving surface of the substrate, the forming method further includes: patterning the light-transmitting layer, forming a plurality of second protrusions on the top of the light-transmitting layer, wherein the lateral and longitudinal dimensions of the second protrusions are both smaller than the wavelength of light.

[0024] Optionally, in the step of forming a plurality of second protrusions on the top of the light-transmitting layer, a spacing between adjacent second protrusions is smaller than a wavelength of light.

[0025] Optionally, in the step of forming a plurality of second protrusions on the top of the light-transmitting layer, the lateral dimensions of the second protrusions gradually increase from the top to the bottom.

[0026] Optionally, the step of patterning the substrate further includes: forming a light-isolating groove in the substrate in an adjacent pixel unit area; and the step of forming a light-transmitting layer covering the light-receiving surface of the substrate further includes: forming a light-isolating structure in the light-isolating groove.

[0027] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0028] In the photoelectric sensor provided by the embodiment of the present invention, in the pixel unit area, a plurality of first protrusions are formed on one side of the light receiving surface of the substrate, the lateral size and the longitudinal size of the first protrusions are both smaller than the wavelength of light, and the light-transmitting layer covers the light receiving surface of the substrate and fills between adjacent first protrusions; in the embodiment of the present invention, since the lateral size and the longitudinal size of the first protrusions are both smaller than the wavelength of light, when light is irradiated on the light receiving surface, the first protrusions have almost no reflection of light, and on the light receiving surface, the light easily regards the first protrusion and the light-transmitting layer between the adjacent first protrusions as the same substance, which is beneficial to reducing the reflection loss of light, increasing the transmission of light on the light receiving surface, effectively increasing the number of transmitted photons, and increasing the collection of light signals, thereby facilitating the improvement of photoelectric detection efficiency.

[0029] In the method for forming a photoelectric sensor provided in an embodiment of the present invention, a patterned substrate is formed, and in a pixel unit area, a plurality of first protrusions are formed on one side of a light receiving surface of the substrate, wherein both the lateral and longitudinal dimensions of the first protrusions are smaller than the wavelength of light, thereby forming a light-transmitting layer covering the light receiving surface of the substrate, and the light-transmitting layer is also filled between adjacent first protrusions. In the embodiment of the present invention, since both the lateral and longitudinal dimensions of the first protrusions are smaller than the wavelength of light, when light is irradiated on the light receiving surface, the first protrusions have almost no reflection of light, and on the light receiving surface, light easily regards the first protrusion and the light-transmitting layer between adjacent first protrusions as the same substance, which is beneficial to reducing the reflection loss of light, increasing the transmission of light on the light receiving surface, effectively increasing the number of transmitted photons, and increasing the collection of optical signals, thereby facilitating the improvement of photoelectric detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure corresponding to a photoelectric sensor;

[0031] Figures 2 to 3 is a schematic structural diagram corresponding to an embodiment of a photoelectric sensor of the present invention;

[0032] Figures 4 to 8It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming a photoelectric sensor of the present invention. DETAILED DESCRIPTION

[0033] As can be seen from the background technology, it is difficult to improve the photoelectric detection efficiency of the currently formed photoelectric sensors.

[0034] Combining a photoelectric sensor, this paper analyzes the reasons why it is difficult to improve the photoelectric detection efficiency of current photoelectric sensors.

[0035] Figure 1 It is a structural schematic diagram corresponding to a photoelectric sensor.

[0036] refer to Figure 1 The photoelectric sensor includes: a substrate 10, the substrate 10 has a light receiving surface 11, and the substrate 10 includes a photosensitive pixel area, the photosensitive pixel area includes a plurality of pixel unit areas 10a distributed in a matrix; a light-transmitting layer 30, covering the light receiving surface 11 of the substrate 10; and a light-isolating structure 21, located in the substrate 10 between adjacent pixel unit areas 10a.

[0037] When light is irradiated on the light receiving surface 11, some photons are lost first due to reflection from the surface of the light-transmitting layer 30 and then due to reflection from the light-receiving surface 11 of the substrate 10. It is difficult for more photons to enter the PN junction in the substrate 10 to trigger avalanche breakdown. The light-transmitting layer 30 and the substrate 10 transmit less light, making it difficult to increase the collection of optical signals, thereby making it difficult to improve the efficiency of photoelectric detection.

[0038] In order to solve the above technical problems, an embodiment of the present invention provides a photoelectric sensor, including: a substrate, the substrate having a light receiving surface, and the substrate including a photosensitive pixel area, the photosensitive pixel area including a plurality of pixel unit areas distributed in a matrix, in which a plurality of first protrusions are formed on one side of the light receiving surface of the substrate, and the lateral and longitudinal dimensions of the first protrusions are both smaller than the wavelength of light; a light-transmitting layer, covering the light receiving surface of the substrate and filling between adjacent first protrusions.

[0039] In the photoelectric sensor provided by the embodiment of the present invention, since the lateral size and longitudinal size of the first protrusion are both smaller than the wavelength of light, when light is irradiated on the light-receiving surface, the first protrusion has almost no reflection of light. On the light-receiving surface, light easily regards the first protrusion and the light-transmitting layer between the adjacent first protrusions as the same substance, which is beneficial to reducing the reflection loss of light, increasing the transmission of light on the light-receiving surface, effectively increasing the number of transmitted photons, and increasing the collection of light signals, thereby facilitating improving the efficiency of photoelectric detection.

[0040] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] Figures 2 to 3It is a structural schematic diagram corresponding to an embodiment of a photoelectric sensor of the present invention.

[0042] Combined with reference Figures 2 to 3 , Figure 2 (a) is a top view of the substrate. Figure 2 (b) Figure 2 (a) is a partial enlarged view of any photosensitive pixel area. Figure 3 for Figure 2 (a) Corresponding cross-sectional view, the photoelectric sensor includes: a substrate 100, the substrate 100 has a light receiving surface 101, and the substrate 100 includes a photosensitive pixel area P, the photosensitive pixel area P includes a plurality of pixel unit areas 100a distributed in a matrix, in the pixel unit area 100a, a plurality of first protrusions 120 are formed on one side of the light receiving surface 101 of the substrate 100, and the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light; a light-transmitting layer 300, covering the light receiving surface 101 of the substrate 100 and filling between adjacent first protrusions 120.

[0043] As an example, in this embodiment, the photoelectric sensor is a DTOF (Direct Time of Flight) sensor.

[0044] In other embodiments, the photoelectric sensor may also be a CCD (Charge Coupled Device) image sensor, a CMOS image sensor, or an iTOF (indirect Time of Flight) sensor, etc.

[0045] In this embodiment, the photoelectric sensor includes: a logic wafer and a pixel wafer bonded to the logic wafer. The substrate 100 is located on the side of the pixel wafer facing away from the logic wafer. The light receiving surface 101 is the side of the pixel wafer facing away from the logic wafer.

[0046] In this embodiment, the substrate 100 of the pixel wafer is a silicon substrate. In other embodiments, the material of the substrate of the pixel wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate of the pixel wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

[0047] The photosensitive pixel area P is used to receive an optical signal so as to convert the optical signal into an electrical signal.

[0048] In the pixel wafer, there are a plurality of photosensitive pixel regions P, which are arranged in a matrix. The pixel unit region 100a is used to form pixels.

[0049] In this embodiment, the pixel wafer has a light receiving surface 101. The light receiving surface 101 refers to a surface for receiving light.

[0050] In this embodiment, the light receiving surface 101 is a first surface; the pixel wafer further includes a second surface 102 opposite to the first surface.

[0051] In this embodiment, the photoelectric sensor is a backside illumination (BSI) photoelectric sensor.

[0052] Correspondingly, in this embodiment, the pixel wafer is a back-illuminated pixel wafer, the light-receiving surface 101 is correspondingly the back surface, and the second surface 102 is the front surface.

[0053] In this embodiment, only a portion of the photosensitive pixel region P and the pixel unit region 100a are shown in the figure, and the pixel unit region 100a may also include a device structure such as a photoelectric element (e.g., a photodiode). Among them, the photodiode may be a back-illuminated single photon avalanche diode (SPAD). For the purpose of simplicity, the detailed structure of the above components is not shown in the embodiment of the present invention.

[0054] In this embodiment, the logic wafer is bonded to the second surface 102 of the pixel wafer.

[0055] The logic wafer is used to analyze and process the electrical signals provided by the pixel wafer.

[0056] By setting the photosensitive pixel area P and the logic area on two wafers respectively and bonding the pixel wafer and the logic wafer together, a larger pixel area can be obtained, which is beneficial for shortening the path of light reaching the photoelectric element, reducing the scattering of light, and making the light more focused, thereby improving the photosensitivity of the photoelectric sensor in a weak light environment and reducing system noise and crosstalk.

[0057] In this embodiment, the substrate 100 of the pixel wafer is used as the first substrate, and the logic wafer has a second substrate 160. The second substrate 160 of the logic wafer may be a silicon substrate. In other embodiments, the material of the second substrate of the logic wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the second substrate of the logic wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

[0058] Accordingly, in this embodiment, a logic transistor (not shown) is also formed in the logic wafer, and the logic transistor is used to perform logic processing on the electrical signal provided by the pixel wafer. Specifically, the logic transistor may include a logic gate structure located on the logic wafer, and a logic drain region and a logic source region located in the logic wafer on both sides of the logic gate structure.

[0059] As an embodiment, the bonding between the second surface 102 of the pixel wafer and the logic wafer is achieved by hybrid bonding.

[0060] Specifically, in this embodiment, a first interconnection layer 180 is formed on the second surface 102 of the pixel wafer, and a second interconnection layer 170 is formed on the second substrate 160 of the logic wafer. The pixel wafer and the logic wafer can be bonded together by using dielectric bonding, and then an electrical connection is made between the first interconnection layer 180 and the second interconnection layer 170.

[0061] The first interconnect layer 180 may include a first metal line, or the first interconnect layer 180 includes a first through silicon via interconnect structure (TSV), or the first interconnect layer 180 includes a first through-hole interconnect structure and a first metal line located on the first through-hole interconnect structure; the second interconnect layer 170 may include a second metal line, or the second interconnect layer 170 includes a second through-hole interconnect structure (TSV), or the second interconnect layer 170 includes a second through-hole interconnect structure and a second metal line located on the second through-hole interconnect structure.

[0062] It should be noted that the above method of bonding the pixel wafer and the logic wafer is only used as an embodiment, and the bonding method between the pixel wafer and the logic wafer is not limited to this. For example: in other embodiments, the bonding method between the pixel wafer and the logic wafer can also be direct bonding (such as melt bonding and anodic bonding) or indirect bonding technology (such as metal eutectic, hot pressing bonding and adhesive bonding).

[0063] The first protrusions 120 are arranged in the pixel unit area 100 a , which is beneficial to improving the optical transmittance of the photosensitive pixel area P, increasing the photoelectric conversion efficiency, and further improving the optical sensitivity performance of the photoelectric sensor.

[0064] Specifically, the first protrusions 120 are arranged above the photoelectric element, and grooves are formed between adjacent first protrusions 120, which can slow down the change in refractive index between the air and the light-receiving surface 101 and reduce the high reflectivity caused by the sudden change in refractive index at the interface, so that more light can enter the photoelectric element and the transmittance of the incident light can be improved. In addition, by setting the first protrusions 120 in the pixel unit area 100a of the light-receiving surface 101, it is also beneficial to disperse the incident light to multiple angles, increase the effective optical path of the light, and correspondingly play a role in trapping light.

[0065] In the present embodiment, since the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light, when light is irradiated on the light receiving surface 101, the first protrusion 120 has almost no reflection of light. On the light receiving surface 101, light easily regards the first protrusion 120 and the light-transmitting layer 300 between the adjacent first protrusions 120 as the same substance, which is beneficial to reduce the reflection loss of light, increase the transmission of light on the light receiving surface 101, effectively increase the number of transmitted photons, increase the collection of optical signals, and thus help improve the efficiency of photoelectric detection.

[0066] Among them, the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light, which means that the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light used when the photoelectric sensor of this embodiment is working. The wavelength of light refers to the distance that the light wave propagates in one vibration cycle. Therefore, if the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light, it is difficult for the first protrusion 120 to reflect light, thereby reducing the reflection loss of light.

[0067] In this embodiment, in the pixel unit region 100 a , the interval d3 between adjacent first protrusions 120 is smaller than the wavelength of light.

[0068] If the spacing d3 between adjacent first protrusions 120 is smaller than the wavelength of light, when light is irradiated on the light receiving surface 101, the light-transmitting layer 300 between adjacent first protrusions 120 has almost no reflection of light. On the light receiving surface 101, light is more likely to regard the first protrusions 120 and the light-transmitting layer 300 between adjacent first protrusions 120 as the same substance, which is further beneficial to reduce the reflection loss of light, further beneficial to increase the transmission of light on the light receiving surface 101, more effectively increase the number of transmitted photons, further beneficial to increase the collection of optical signals, and thus beneficial to improve the efficiency of photoelectric detection.

[0069] In this embodiment, the transverse dimension d1 of the first protrusion 120 gradually increases from the top to the bottom.

[0070] The lateral dimension d1 of the first protrusion 120 gradually increases from the top to the bottom. The film layer formed by the light-transmitting layer 300 between the first protrusion 120 and the adjacent first protrusion 120 can be regarded as a layer of thin film with a gradually changing refractive index, so that when light passes through the light-receiving surface 101 and enters the substrate 100, a smooth and gradual refractive index change can be obtained, which greatly reduces the high reflectivity caused by the sudden change of the refractive index at the interface, so that more light can enter the photoelectric element, improve the transmittance of the incident light, and play a transmittance-enhancing role.

[0071] In this embodiment, the shape of the first protrusion 120 is not limited. Specifically, as an example, in this embodiment, the shape of the first protrusion 120 includes a cylinder, a truncated cone, a prism or a cuboid.

[0072] In this embodiment, in the pixel unit area 100 a , a plurality of first protrusions 120 are distributed in an array.

[0073] The plurality of first protrusions 120 are arranged in an array in the pixel unit area 100a, which is not only beneficial to the design and layout of the layout, but also beneficial to maximizing the number of first protrusions 120 in a single pixel unit area 100a, thereby further increasing the density of the first protrusions 120 and improving the uniformity of the film layer formed by the light-transmitting layer 300 between the first protrusions 120 and the adjacent first protrusions 120.

[0074] In other embodiments, in the pixel unit area, the first protrusions may not be arranged in an array, but may be arranged in other ways in the pixel unit area, for example, in a scattered arrangement, a staggered arrangement, or a grid-like connection.

[0075] The light-transmitting layer 300 has a light-transmitting property and is formed on the light-receiving surface 101 , so that light can pass through the light-transmitting layer 300 and enter the light-receiving surface 101 and the substrate 100 thereunder, so that the optoelectronic element can work normally.

[0076] In this embodiment, the material of the light-transmitting layer 300 is a light-transmitting material, and the material of the light-transmitting layer 300 is an insulating material to prevent the electrical properties of the photoelectric sensor from being affected. In this embodiment, the material of the light-transmitting layer 300 includes silicon oxide, silicon nitride, silicon oxynitride or silicon carbide. As an example, the material of the light-transmitting layer 300 is silicon oxide. Silicon oxide has high process compatibility and low cost, and silicon oxide has good light transmission and insulation properties.

[0077] In this embodiment, a plurality of second protrusions 310 are formed on the top of the light-transmitting layer 300 , and a transverse dimension d4 and a longitudinal dimension d5 of the second protrusions 310 are both smaller than the wavelength of light.

[0078] The second protrusions 310 are helpful to improve the optical transmittance of the photosensitive pixel area P, increase the photoelectric conversion efficiency, and thus improve the optical sensitivity performance of the photoelectric sensor. Moreover, multiple second protrusions 310 are arranged on the surface of the light-transmitting layer 300, and also have a water-repelling effect, which is also helpful to avoid condensation of water vapor on the surface of the light-transmitting layer 300 as much as possible.

[0079] Specifically, the second protrusions 310 are arranged above the photoelectric element, and grooves are formed between adjacent second protrusions 310, which can slow down the change in refractive index between the air and the surface of the light-transmitting layer 300, reduce the high reflectivity caused by the sudden change in refractive index at the interface, so that more light can enter the light-transmitting layer 300 and improve the transmittance of the incident light.

[0080] In the present embodiment, since the lateral dimension d4 and the longitudinal dimension d5 of the second protrusion 310 are both smaller than the wavelength of light, when light is irradiated on the surface of the light-transmitting layer 300, the second protrusion 310 has almost no reflection of light. On the surface of the light-transmitting layer 300, light easily regards the second protrusion 310 and the light-transmitting layer 300 between adjacent second protrusions 310 as the same substance, which is beneficial to reducing the reflection loss of light, increasing the transmission of light on the light-transmitting layer 300, effectively increasing the number of transmitted photons, and increasing the collection of optical signals, thereby facilitating the improvement of photoelectric detection efficiency.

[0081] In this embodiment, the interval d6 between adjacent second protrusions 310 is smaller than the wavelength of light.

[0082] If the spacing d6 between adjacent second protrusions 310 is smaller than the wavelength of light, when light is irradiated on the light-transmitting layer 300, it is easier for light to regard the second protrusions 310 and the air between adjacent second protrusions 310 as the same substance, which is further beneficial to reduce the reflection loss of light, further beneficial to increase the transmission of light on the surface of the light-transmitting layer 300, more effectively increase the number of transmitted photons, further beneficial to increase the collection of light signals, and thus beneficial to improve the efficiency of photoelectric detection.

[0083] In this embodiment, the transverse dimension d4 of the second protrusion 310 gradually increases from the top to the bottom.

[0084] The lateral dimension d4 of the second protrusion 310 gradually increases from the top to the bottom. The film layer formed by the air between the second protrusion 310 and the adjacent second protrusion 310 can be regarded as a layer of thin film with a gradually changing refractive index. Therefore, when light enters the light-transmitting layer 300, a smooth and gradual refractive index change can be obtained, which greatly reduces the high reflectivity caused by the sudden change of the refractive index at the interface, so that more light can enter the photoelectric element, improve the transmittance of the incident light, and play a transmittance-enhancing role.

[0085] In this embodiment, the shape of the second protrusion 310 is not limited. Specifically, as an example, in this embodiment, the shape of the second protrusion 310 includes a cylinder, a truncated cone, a prism or a cuboid.

[0086] In this embodiment, a plurality of second protrusions 310 are distributed in an array.

[0087] The plurality of second protrusions 310 are arranged in an array, which is not only beneficial to the design and layout of the layout, but also beneficial to maximizing the number of second protrusions 310, thereby further increasing the density of the second protrusions 310 and improving the uniformity of the film layer formed by the air between the second protrusions 310 and the adjacent second protrusions 310.

[0088] In other embodiments, the second protrusions may not be arranged in an array, but may be arranged in other ways, for example, in a scattered arrangement, a staggered arrangement, or in a grid-like connection.

[0089] In this embodiment, the photoelectric sensor further includes: a doping region 110 located in the substrate 100 in the pixel unit region 100 a .

[0090] During the operation of the photoelectric sensor, the generated electrons move toward the doping region 110 , and the doping region 110 is used to accumulate electrons during the photoelectric conversion process.

[0091] Specifically, in the present embodiment, the doping type of the doping region 110 is N-type, and the doping ions of the N-type doping region are N-type ions, which include P ions, As ions, or Sb ions.

[0092] The N-type doped region is connected to a high potential during the operation of the photoelectric sensor. The majority carriers in the N-type doped region are electrons, and the concentration of free electrons is much greater than the concentration of holes. Therefore, the N-type doped region is an area for accumulating electrons.

[0093] The N-type doped region, as the main photogenerated carrier generation and storage region, is located below the first protrusion 120. The first protrusion 120 above the N-type doped region can effectively increase the photogenerated carrier generation efficiency, which is beneficial to improving the performance of the photoelectric sensor.

[0094] In this embodiment, the photoelectric sensor further includes: a light isolation structure 210 located in the substrate 100 adjacent to the pixel unit area 100 a.

[0095] The light isolation structure 210 is used to prevent optical crosstalk between adjacent pixels.

[0096] Specifically, the light-isolating structure 210 has a shielding effect on light. The light-isolating structure 210 is located between the light-transmitting layers 300 of adjacent pixel unit areas 100a. When the incident light irradiates the photosensitive pixel area P, the incident light will only enter the corresponding pixel unit area 100a through the light-transmitting layer 300, and cannot pass through the light-isolating structure 210 around the light-transmitting layer 300 to enter other adjacent pixel unit areas 100a, thereby avoiding optical crosstalk to other pixel unit areas 100a.

[0097] In this embodiment, the light isolation structure 210 is made of a conductive material, which is usually opaque, thereby satisfying the light isolation function of the light isolation structure 210 .

[0098] As an example, the conductive material may be a metal material. Specifically, the material of the light isolation structure 210 includes one or more of W, Al, Cu, Ti, TiN, Ta, and TaN. In this embodiment, the material of the light isolation structure 210 is W.

[0099] In other embodiments, the conductive material may also be polysilicon doped with conductive ions.

[0100] Figures 4 to 8 It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming a photoelectric sensor of the present invention.

[0101] Combined with reference Figure 4 and Figure 5 , Figure 4 (a) is a top view of the substrate. Figure 4 (b) Figure 4 (a) is a partial enlarged view of any photosensitive pixel area. Figure 5 for Figure 4 (a) is a corresponding cross-sectional view, providing a substrate 100, the substrate 100 has a light receiving surface 101, and the substrate 100 includes a photosensitive pixel area P, and the photosensitive pixel area P includes a plurality of pixel unit areas 100a distributed in a matrix.

[0102] As an example, in this embodiment, the photoelectric sensor is a DTOF (Direct Time of Flight) sensor.

[0103] In other embodiments, the photoelectric sensor may also be a CCD (Charge Coupled Device) image sensor, a CMOS image sensor, or an iTOF (indirect Time of Flight) sensor, etc.

[0104] In this embodiment, the photoelectric sensor includes: a logic wafer and a pixel wafer bonded to the logic wafer. The substrate 100 is located on the side of the pixel wafer facing away from the logic wafer. The light receiving surface 101 is the side of the pixel wafer facing away from the logic wafer.

[0105] In this embodiment, the substrate 100 of the pixel wafer is a silicon substrate. In other embodiments, the material of the substrate of the pixel wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate of the pixel wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

[0106] The photosensitive pixel area P is used to receive an optical signal so as to convert the optical signal into an electrical signal.

[0107] In the pixel wafer, there are a plurality of photosensitive pixel regions P, which are arranged in a matrix. The pixel unit region 100a is used to form pixels.

[0108] In this embodiment, the pixel wafer has a light receiving surface 101. The light receiving surface 101 refers to a surface for receiving light.

[0109] In this embodiment, the light receiving surface 101 is a first surface; the pixel wafer further includes a second surface 102 opposite to the first surface.

[0110] In this embodiment, the photoelectric sensor is a backside illumination (BSI) photoelectric sensor.

[0111] Correspondingly, in this embodiment, the pixel wafer is a back-illuminated pixel wafer, the light-receiving surface 101 is correspondingly the back surface, and the second surface 102 is the front surface.

[0112] In this embodiment, only a portion of the photosensitive pixel region P and the pixel unit region 100a are shown in the figure, and the pixel unit region 100a may also include a device structure such as a photoelectric element (e.g., a photodiode). Among them, the photodiode may be a back-illuminated single photon avalanche diode (SPAD). For the purpose of simplicity, the detailed structure of the above components is not shown in the embodiment of the present invention.

[0113] In this embodiment, the logic wafer is bonded to the second surface 102 of the pixel wafer.

[0114] The logic wafer is used to analyze and process the electrical signals provided by the pixel wafer.

[0115] By setting the photosensitive pixel area P and the logic area on two wafers respectively and bonding the pixel wafer and the logic wafer together, a larger pixel area can be obtained, which is beneficial for shortening the path of light reaching the photoelectric element, reducing the scattering of light, and making the light more focused, thereby improving the photosensitivity of the photoelectric sensor in a weak light environment and reducing system noise and crosstalk.

[0116] In this embodiment, the substrate 100 of the pixel wafer is used as the first substrate, and the logic wafer has a second substrate 160. The second substrate 160 of the logic wafer may be a silicon substrate. In other embodiments, the material of the second substrate of the logic wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the second substrate of the logic wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

[0117] Accordingly, in this embodiment, a logic transistor (not shown) is also formed in the logic wafer, and the logic transistor is used to perform logic processing on the electrical signal provided by the pixel wafer. Specifically, the logic transistor may include a logic gate structure located on the logic wafer, and a logic drain region and a logic source region located in the logic wafer on both sides of the logic gate structure.

[0118] As an embodiment, the bonding between the second surface 102 of the pixel wafer and the logic wafer is achieved by hybrid bonding.

[0119] Specifically, in this embodiment, a first interconnection layer 180 is formed on the second surface 102 of the pixel wafer, and a second interconnection layer 170 is formed on the second substrate 160 of the logic wafer. The pixel wafer and the logic wafer can be bonded together by using dielectric bonding, and then an electrical connection is made between the first interconnection layer 180 and the second interconnection layer 170.

[0120] Among them, the first interconnection layer 180 may include a first metal line, or the first interconnection layer 180 includes a first through silicon via interconnection structure (TSV), or the first interconnection layer 180 includes a first through-hole interconnection structure and a first metal line located on the first through-hole interconnection structure; the second interconnection layer 170 may include a second metal line, or the second interconnection layer 170 is a second through-hole interconnection structure (TSV), or the second interconnection layer 170 includes a second through-hole interconnection structure and a second metal line located on the second through-hole interconnection structure.

[0121] It should be noted that the above method of bonding the pixel wafer and the logic wafer is only used as an embodiment, and the bonding method between the pixel wafer and the logic wafer is not limited to this. For example: in other embodiments, the bonding method between the pixel wafer and the logic wafer can also be direct bonding (such as melt bonding and anodic bonding) or indirect bonding technology (such as metal eutectic, hot pressing bonding and adhesive bonding).

[0122] In this embodiment, in the step of providing the substrate 100 , a doping region 110 is further formed in the substrate 100 , and is located in the substrate 100 in the pixel unit region 100 a .

[0123] During the operation of the photoelectric sensor, the generated electrons move toward the doping region 110 , and the doping region 110 is used to accumulate electrons during the photoelectric conversion process.

[0124] Specifically, in the present embodiment, the doping type of the doping region 110 is N-type, and the doping ions of the N-type doping region are N-type ions, which include P ions, As ions, or Sb ions.

[0125] The N-type doped region is connected to a high potential during the operation of the photoelectric sensor. The majority carriers in the N-type doped region are electrons, and the concentration of free electrons is much greater than the concentration of holes. Therefore, the N-type doped region is an area for accumulating electrons.

[0126] The N-type doped region, as the main photogenerated carrier generation and storage region, is located below the first protrusion 120. The first protrusion 120 above the N-type doped region can effectively increase the photogenerated carrier generation efficiency, which is beneficial to improving the performance of the photoelectric sensor.

[0127] refer to Figure 6 , the patterned substrate 100, in the pixel unit area 100a, a plurality of first protrusions 120 are formed on one side of the light receiving surface 101 of the substrate 100, and the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light.

[0128] The first protrusions 120 are arranged in the pixel unit area 100 a , which is beneficial to improving the optical transmittance of the photosensitive pixel area P, increasing the photoelectric conversion efficiency, and further improving the optical sensitivity performance of the photoelectric sensor.

[0129] Specifically, the first protrusions 120 are arranged above the photoelectric element, and grooves are formed between adjacent first protrusions 120, which can slow down the change in refractive index between the air and the light-receiving surface 101 and reduce the high reflectivity caused by the sudden change in refractive index at the interface, so that more light can enter the photoelectric element and the transmittance of the incident light can be improved. In addition, by setting the first protrusions 120 in the pixel unit area 100a of the light-receiving surface 101, it is also beneficial to disperse the incident light to multiple angles, increase the effective optical path of the light, and correspondingly play a role in trapping light.

[0130] In the present embodiment, since the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light, when light is irradiated on the light receiving surface 101, the first protrusion 120 has almost no reflection of light. On the light receiving surface 101, light easily regards the first protrusion 120 and the light-transmitting layer 300 between the adjacent first protrusions 120 as the same substance, which is beneficial to reduce the reflection loss of light, increase the transmission of light on the light receiving surface 101, effectively increase the number of transmitted photons, increase the collection of optical signals, and thus help improve the efficiency of photoelectric detection.

[0131] Among them, the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light, which means that the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light used when the photoelectric sensor of this embodiment is working. The wavelength of light refers to the distance that the light wave propagates in one vibration cycle. Therefore, if the lateral dimension d1 and the longitudinal dimension d2 of the first protrusion 120 are both smaller than the wavelength of light, it is difficult for the first protrusion 120 to reflect light, thereby reducing the reflection loss of light.

[0132] In this embodiment, in the step of forming a plurality of first protrusions 120 on the light receiving surface 101 of the substrate 100 , in the pixel unit region 100 a , the interval d3 between adjacent first protrusions 120 is smaller than the wavelength of light.

[0133] If the spacing d3 between adjacent first protrusions 120 is smaller than the wavelength of light, when light is irradiated on the light receiving surface 101, the light-transmitting layer 300 between adjacent first protrusions 120 has almost no reflection of light. On the light receiving surface 101, light is more likely to regard the first protrusions 120 and the light-transmitting layer 300 between adjacent first protrusions 120 as the same substance, which is further beneficial to reduce the reflection loss of light, further beneficial to increase the transmission of light on the light receiving surface 101, more effectively increase the number of transmitted photons, further beneficial to increase the collection of optical signals, and thus beneficial to improve the efficiency of photoelectric detection.

[0134] In this embodiment, in the step of forming a plurality of first protrusions 120 on one side of the light receiving surface 101 of the substrate 100 , the lateral dimension d1 of the first protrusion 120 gradually increases from the top to the bottom.

[0135] The lateral dimension d1 of the first protrusion 120 gradually increases from the top to the bottom. The film layer formed by the light-transmitting layer 300 between the first protrusion 120 and the adjacent first protrusion 120 can be regarded as a layer of thin film with a gradually changing refractive index, so that when light passes through the light-receiving surface 101 and enters the substrate 100, a smooth and gradual refractive index change can be obtained, which greatly reduces the high reflectivity caused by the sudden change of the refractive index at the interface, so that more light can enter the photoelectric element, improve the transmittance of the incident light, and play a transmittance-enhancing role.

[0136] In this embodiment, the morphology of the first protrusion 120 is not limited. Specifically, as an example, in this embodiment, in the step of forming a plurality of first protrusions 120 on one side of the light receiving surface 101 of the substrate 100, the morphology of the first protrusion 120 includes a cylinder, a truncated cone, a prism or a cuboid.

[0137] In this embodiment, in the step of forming a plurality of first protrusions 120 on one side of the light receiving surface 101 of the substrate 100 , the plurality of first protrusions 120 are distributed in an array in the pixel unit region 100 a .

[0138] The plurality of first protrusions 120 are arranged in an array in the pixel unit area 100a, which is not only beneficial to the design and layout of the layout, but also beneficial to maximizing the number of first protrusions 120 in a single pixel unit area 100a, thereby further increasing the density of the first protrusions 120 and improving the uniformity of the film layer formed by the light-transmitting layer 300 between the first protrusions 120 and the adjacent first protrusions 120.

[0139] In other embodiments, in the pixel unit area, the first protrusions may not be arranged in an array, but may be arranged in other ways in the pixel unit area, for example, in a scattered arrangement, a staggered arrangement, or a grid-like connection.

[0140] Specifically, in this embodiment, the step of forming a plurality of first protrusions 120 on one side of the light receiving surface 101 of the substrate 100 includes: forming a mask layer on the light receiving surface 101, wherein a mask opening is formed in the mask layer and is located in the pixel unit area 100a and exposes the light receiving surface 101; and patterning the substrate 100 along the mask opening to form a plurality of first protrusions 120.

[0141] In this embodiment, a plurality of first protrusions 120 are formed on the light receiving surface 101 of the substrate 100 by using a dry etching process.

[0142] The dry etching process has the characteristic of anisotropic etching. Therefore, by selecting the dry etching process, the etching is more directional, which is beneficial to improving the dimensional accuracy of the first protrusion 120.

[0143] In this embodiment, after the first protrusion 120 is formed, the method further includes: removing the mask layer to expose the light receiving surface 101 .

[0144] In this embodiment, the step of patterning the substrate 100 further includes: forming a light-isolating groove in the substrate 100 adjacent to the pixel unit region 100 a.

[0145] The light-isolating groove is used to provide a spatial position for the subsequent formation of a light-isolating structure.

[0146] refer to Figure 7 , forming a light-transmitting layer 300 covering the light-receiving surface 101 of the substrate 100 , and the light-transmitting layer 300 is also filled between adjacent first protrusions 120 .

[0147] The light-transmitting layer 300 has a light-transmitting property and is formed on the light-receiving surface 101 , so that light can pass through the light-transmitting layer 300 and enter the light-receiving surface 101 and the substrate 100 thereunder, so that the optoelectronic element can work normally.

[0148] In this embodiment, the material of the light-transmitting layer 300 is a light-transmitting material, and the material of the light-transmitting layer 300 is an insulating material to prevent the electrical properties of the photoelectric sensor from being affected. In this embodiment, the material of the light-transmitting layer 300 includes silicon oxide, silicon nitride, silicon oxynitride or silicon carbide. As an example, the material of the light-transmitting layer 300 is silicon oxide. Silicon oxide has high process compatibility and low cost, and silicon oxide has good light transmission and insulation properties.

[0149] In this embodiment, the step of forming the light-transmitting layer 300 covering the light-receiving surface 101 of the substrate 100 further includes: forming a light-isolating structure 210 in the light-isolating groove.

[0150] The light isolation structure 210 is used to prevent optical crosstalk between adjacent pixels.

[0151] Specifically, the light-isolating structure 210 has a shielding effect on light. The light-isolating structure 210 is located between the light-transmitting layers 300 of adjacent pixel unit areas 100a. When the incident light irradiates the photosensitive pixel area P, the incident light will only enter the corresponding pixel unit area 100a through the light-transmitting layer 300, and cannot pass through the light-isolating structure 210 around the light-transmitting layer 300 to enter other adjacent pixel unit areas 100a, thereby avoiding optical crosstalk to other pixel unit areas 100a.

[0152] In this embodiment, the light isolation structure 210 is made of a conductive material, which is usually opaque, thereby satisfying the light isolation function of the light isolation structure 210 .

[0153] As an example, the conductive material may be a metal material. Specifically, the material of the light isolation structure 210 includes one or more of W, Al, Cu, Ti, TiN, Ta, and TaN. In this embodiment, the material of the light isolation structure 210 is W.

[0154] In other embodiments, the conductive material may also be polysilicon doped with conductive ions.

[0155] refer to Figure 8 After forming a light-transmitting layer 300 covering the light-receiving surface 101 of the substrate 100, the forming method further includes: patterning the light-transmitting layer 300, forming a plurality of second protrusions 310 on the top of the light-transmitting layer 300, and the lateral dimension d4 and the longitudinal dimension d5 of the second protrusion 310 are both smaller than the wavelength of light.

[0156] The second protrusions 310 are helpful to improve the optical transmittance of the photosensitive pixel area P, increase the photoelectric conversion efficiency, and thus improve the optical sensitivity performance of the photoelectric sensor. Moreover, multiple second protrusions 310 are arranged on the surface of the light-transmitting layer 300, and also have a water-repelling effect, which is also helpful to avoid condensation of water vapor on the surface of the light-transmitting layer 300 as much as possible.

[0157] Specifically, the second protrusions 310 are arranged above the photoelectric element, and grooves are formed between adjacent second protrusions 310, which can slow down the change in refractive index between the air and the surface of the light-transmitting layer 300, reduce the high reflectivity caused by the sudden change in refractive index at the interface, so that more light can enter the light-transmitting layer 300 and improve the transmittance of the incident light.

[0158] In the present embodiment, since the lateral dimension d4 and the longitudinal dimension d5 of the second protrusion 310 are both smaller than the wavelength of light, when light is irradiated on the surface of the light-transmitting layer 300, the second protrusion 310 has almost no reflection of light. On the surface of the light-transmitting layer 300, light easily regards the second protrusion 310 and the light-transmitting layer 300 between adjacent second protrusions 310 as the same substance, which is beneficial to reducing the reflection loss of light, increasing the transmission of light on the light-transmitting layer 300, effectively increasing the number of transmitted photons, and increasing the collection of optical signals, thereby facilitating the improvement of photoelectric detection efficiency.

[0159] In this embodiment, in the step of forming a plurality of second protrusions 310 on the top of the light-transmitting layer 300 , the interval d6 between adjacent second protrusions 310 is smaller than the wavelength of light.

[0160] If the spacing d6 between adjacent second protrusions 310 is smaller than the wavelength of light, when light is irradiated on the light-transmitting layer 300, it is easier for light to regard the second protrusions 310 and the air between adjacent second protrusions 310 as the same substance, which is further beneficial to reduce the reflection loss of light, further beneficial to increase the transmission of light on the surface of the light-transmitting layer 300, more effectively increase the number of transmitted photons, further beneficial to increase the collection of light signals, and thus beneficial to improve the efficiency of photoelectric detection.

[0161] In this embodiment, in the step of forming a plurality of second protrusions 310 on the top of the light-transmitting layer 300 , the lateral dimension d4 of the second protrusions 310 gradually increases from the top to the bottom.

[0162] The lateral dimension d4 of the second protrusion 310 gradually increases from the top to the bottom. The film layer formed by the air between the second protrusion 310 and the adjacent second protrusion 310 can be regarded as a layer of thin film with a gradually changing refractive index. Therefore, when light enters the light-transmitting layer 300, a smooth and gradual refractive index change can be obtained, which greatly reduces the high reflectivity caused by the sudden change of the refractive index at the interface, so that more light can enter the photoelectric element, improve the transmittance of the incident light, and play a transmittance-enhancing role.

[0163] In this embodiment, the morphology of the second protrusion 310 is not limited. Specifically, as an example, in this embodiment, in the step of forming a plurality of second protrusions 310 on the top of the light-transmitting layer 300, the morphology of the second protrusion 310 includes a cylinder, a truncated cone, a prism or a cuboid.

[0164] In this embodiment, in the step of forming a plurality of second protrusions 310 on the top of the light-transmitting layer 300 , the plurality of second protrusions 310 are distributed in an array.

[0165] The plurality of second protrusions 310 are arranged in an array, which is not only beneficial to the design and layout of the layout, but also beneficial to maximizing the number of second protrusions 310, thereby further increasing the density of the second protrusions 310 and improving the uniformity of the film layer formed by the air between the second protrusions 310 and the adjacent second protrusions 310.

[0166] In other embodiments, the second protrusions may not be arranged in an array, but may be arranged in other ways, for example, in a scattered arrangement, a staggered arrangement, or in a grid-like connection.

[0167] In this embodiment, the light-transmitting layer 300 is patterned by a dry etching process, and a plurality of second protrusions 310 are formed on the top of the light-transmitting layer 300 .

[0168] The dry etching process has the characteristic of anisotropic etching. Therefore, by selecting the dry etching process, the etching is more directional, which is beneficial to improving the dimensional accuracy of the second protrusion 310 .

[0169] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A photoelectric sensor, characterized in that: include: A substrate, wherein the substrate has a light-receiving surface, and the substrate includes a photosensitive pixel area, the photosensitive pixel area includes a plurality of pixel unit areas distributed in a matrix, in the pixel unit area, a plurality of first protrusions are formed on one side of the light-receiving surface of the substrate, and the lateral size and the longitudinal size of the first protrusion are both smaller than the wavelength of light; The light-transmitting layer covers the light-receiving surface of the substrate and is filled between adjacent first protrusions.

2. The photoelectric sensor according to claim 1, characterized in that In the pixel unit area, a distance between adjacent first protrusions is smaller than a wavelength of light.

3. The photoelectric sensor according to claim 1, wherein: In the pixel unit area, a plurality of the first protrusions are distributed in an array.

4. The photoelectric sensor according to claim 1, wherein: The shape of the first protrusion includes a cylinder, a truncated cone, a prism or a cuboid.

5. The photoelectric sensor according to claim 1, wherein: The lateral dimension of the first protrusion gradually increases from the top to the bottom.

6. The photoelectric sensor according to claim 1, wherein: A plurality of second protrusions are formed on the top of the light-transmitting layer, and the lateral and longitudinal dimensions of the second protrusions are both smaller than the wavelength of light.

7. The photoelectric sensor according to claim 6, characterized in that The interval between adjacent second protrusions is smaller than the wavelength of light.

8. The photoelectric sensor according to claim 6, wherein: A plurality of the second protrusions are distributed in an array.

9. The photoelectric sensor according to claim 6, wherein: The second protrusion has a shape including a cylinder, a truncated cone, a prism or a cuboid.

10. The photoelectric sensor according to claim 6, characterized in that The lateral dimension of the second protrusion gradually increases from the top to the bottom.

11. The photoelectric sensor according to claim 1, wherein: The photoelectric sensor further includes a light isolation structure located in a substrate adjacent to the pixel unit area.

12. The photoelectric sensor according to claim 1, wherein: The photoelectric sensor is a back-illuminated photoelectric sensor.

13. A method for forming a photoelectric sensor, characterized in that: include: Providing a substrate, wherein the substrate has a light-receiving surface, and the substrate includes a photosensitive pixel area, wherein the photosensitive pixel area includes a plurality of pixel unit areas distributed in a matrix; Patterning the substrate, forming a plurality of first protrusions on one side of the light-receiving surface of the substrate in the pixel unit area, wherein the lateral and longitudinal dimensions of the first protrusions are both smaller than the wavelength of light; A light-transmitting layer is formed to cover the light-receiving surface of the substrate, and the light-transmitting layer is also filled between adjacent first protrusions.

14. The method for forming a photoelectric sensor according to claim 13, wherein: In the step of forming a plurality of first protrusions on one side of the light receiving surface of the substrate, in the pixel unit area, a distance between adjacent first protrusions is smaller than a wavelength of light.

15. The method for forming a photoelectric sensor according to claim 13, wherein: In the step of forming a plurality of first protrusions on one side of the light receiving surface of the substrate, the lateral dimensions of the first protrusions gradually increase from the top to the bottom.

16. The method for forming a photoelectric sensor according to claim 13, wherein: A plurality of first protrusions are formed on one side of the light receiving surface of the substrate by using a dry etching process.

17. The method for forming a photoelectric sensor according to claim 13, wherein: After forming a light-transmitting layer covering the light-receiving surface of the substrate, the forming method further includes: patterning the light-transmitting layer, forming a plurality of second protrusions on the top of the light-transmitting layer, wherein the lateral and longitudinal dimensions of the second protrusions are both smaller than the wavelength of light.

18. The method for forming a photoelectric sensor according to claim 17, wherein: In the step of forming a plurality of second protrusions on the top of the light-transmitting layer, a distance between adjacent second protrusions is smaller than a wavelength of light.

19. The method for forming a photoelectric sensor according to claim 17, wherein: In the step of forming a plurality of second protrusions on the top of the light-transmitting layer, the lateral dimensions of the second protrusions gradually increase from the top to the bottom.

20. The method for forming a photoelectric sensor according to claim 13, wherein: The step of patterning the substrate further includes: forming a light-isolating groove in the substrate adjacent to the pixel unit area; The step of forming a light-transmitting layer covering the light-receiving surface of the substrate further includes: forming a light-isolating structure in the light-isolating groove.

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