Photoelectric sensor, forming method of photoelectric sensor, image sensor and forming method of image sensor

Abstract

The invention discloses a photoelectric sensor and a forming method thereof, and an image sensor and a forming method thereof, and the photoelectric sensor comprises a substrate which comprises a photosensitive region and an isolation region surrounding the photosensitive region; a photosensitive structure located in the photosensitive region; the optical waveguide structure is positioned on the substrate; the isolation groove is located in the isolation area and the optical waveguide structure, the isolation groove surrounds the photosensitive area, the isolation groove comprises a first part and a second part located on the first part, the second part is located in the optical waveguide structure, and the first part is located in the isolation area; the reflecting layer is positioned on the side wall of the second part; the isolation structure is located in the isolation groove and further located on the surface of the reflecting layer, and the refractive index of the material of the reflecting layer is smaller than that of the material of the isolation structure. The performance of the photoelectric sensor is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to a photoelectric sensor and a forming method thereof, an image sensor and a forming method thereof. Background Art

[0002] Photoelectric sensors are devices that can convert light signals into electrical signals based on the photoelectric effect. The basic working principle is that when light shines on certain substances, the electrons of the substances absorb the energy of photons, and a corresponding electrical effect can occur to detect the light signal. Due to the unique advantage of efficient photon transmission, photoelectric sensors have broad application prospects in laser ranging, three-dimensional imaging, quantum transmission, etc.

[0003] Photoelectric sensors are usually composed of a pixel area (pixel) and a logic circuit area (logic). The pixel area is used to receive optical signals, and the logic circuit area is responsible for processing the converted electrical signals. Among them, the photon detection efficiency (PDE) of the pixel area is a crucial factor affecting the performance of photoelectric sensors. The higher the photon detection efficiency of the pixel area, the better the optical sensitivity performance of the photoelectric sensor, and the more comprehensive the electrical signal obtained, so that more detailed ranging and imaging information can be obtained in the end.

[0004] Single photon avalanche diode (SPAD) detectors have become a mainstream device that has attracted widespread attention due to their high sensitivity and picosecond time response. Usually, SPADs are arranged into different arrays to form SiPMs (silicon photodiodes) according to usage requirements, in which each SPAD works independently. When the size of the pixel area becomes smaller, the anti-interference ability of SPADs decreases, which will cause erroneous light signal sensing, that is, light crosstalk. To improve the accuracy of detection, researchers designed an isolation structure between two SPADs to block the light signal. However, the isolation structure will occupy the effective photosensitive area of ​​the pixel area, and as the chip size decreases, the proportion of the occupied effective photosensitive area increases. This will reduce the photon detection efficiency of the photoelectric sensor.

[0005] Therefore, it is necessary to improve the photon detection efficiency of the photoelectric sensor while preventing optical signal crosstalk. Summary of the invention

[0006] The technical problem solved by the present invention is to provide a photoelectric sensor and a method for forming the same, an image sensor and a method for forming the same, so as to improve the photon detection efficiency of the photoelectric sensor.

[0007] To solve the above technical problems, the technical solution of the present invention provides a photoelectric sensor, comprising: a substrate, the substrate comprising a photosensitive area and an isolation area surrounding the photosensitive area; a photosensitive structure located in the photosensitive area; an optical waveguide structure located on the substrate; an isolation groove located in the isolation area and in the optical waveguide structure, the isolation groove surrounds the photosensitive area, the isolation groove comprises a first part and a second part located on the first part, the second part is located in the optical waveguide structure, and the first part is located in the isolation area; a reflective layer located on the side wall of the second part; an isolation structure located in the isolation groove, the isolation structure is also located on the surface of the reflective layer, and the refractive index of the reflective layer material is less than the refractive index of the isolation structure material.

[0008] Optionally, the refractive index of the reflective layer material is smaller than the refractive index of the optical waveguide structure material.

[0009] Optionally, the material of the reflective layer includes aluminum, copper, silver, gold tungsten, magnesium oxide or aluminum oxide.

[0010] Optionally, the isolation structure includes a first isolation layer located in the first part and a second isolation layer located in the second part, and the first isolation layer and the second isolation layer are made of the same material; the material of the isolation structure includes silicon nitride, silicon oxide or polysilicon.

[0011] Optionally, a depth of the isolation groove in the isolation region is greater than a depth of the photosensitive structure.

[0012] Optionally, the photosensitive structure includes a first doping region and a second doping region located on the first doping region, the conductivity type of the first doping region and the conductivity type of the second doping region are opposite to each other, and the surface of the substrate exposes the surface of the second doping region.

[0013] Optionally, the conductivity type of the first doping region includes N-type or P-type; the conductivity type of the second doping region includes N-type or P-type.

[0014] Optionally, it also includes: a first conductive structure located in the optical waveguide structure, the first conductive structure is electrically connected to the photosensitive structure; and a second conductive structure located in the optical waveguide structure, the second conductive structure is located on the first conductive structure and is electrically connected to the first conductive structure.

[0015] Optionally, it further includes: a first protective layer located on the substrate, the optical waveguide structure is located on the first protective layer, and the material of the first protective layer is different from that of the optical waveguide structure; and the first part is located in the isolation region and in the first protective layer.

[0016] Correspondingly, the technical solution of the present invention also provides an image sensor, including: a substrate, the substrate including a pixel area and a logic area, the pixel area including a photosensitive area and an isolation area surrounding the photosensitive area; a photosensitive structure located in the photosensitive area; an optical waveguide structure located on the substrate; an isolation groove located in the isolation area and in the optical waveguide structure, the isolation groove surrounds the photosensitive area, the isolation groove includes a first part and a second part located on the first part, the second part is located in the optical waveguide structure, and the first part is located in the isolation area; a reflective layer located on the side wall of the second part; an isolation structure located in the isolation groove, the isolation structure is also located on the surface of the reflective layer, the refractive index of the reflective layer material is less than the refractive index of the isolation structure material; a filter structure located on the pixel area; a lens structure located on the filter structure.

[0017] Correspondingly, the technical solution of the present invention also provides a method for forming a photoelectric sensor, comprising: providing a substrate, the substrate comprising a photosensitive area and an isolation area surrounding the photosensitive area; forming a photosensitive structure in the photosensitive area; forming an optical waveguide structure on the substrate; forming an isolation groove in the optical waveguide structure and in the isolation area, the isolation groove surrounding the photosensitive area, the isolation groove comprising a first part and a second part located on the first part, the second part being located in the optical waveguide structure, and the first part being located in the isolation area; forming a reflective layer on the side wall of the second part and forming an isolation structure in the isolation groove, the isolation structure being also located on the surface of the reflective layer, and the refractive index of the reflective layer material being less than the refractive index of the isolation structure material.

[0018] Optionally, before the isolation trench is formed in the isolation region, the refractive index of the reflective layer material is smaller than the refractive index of the optical waveguide structure material.

[0019] Optionally, before forming the isolation grooves in the optical waveguide structure and in the isolation region, the method further includes: forming a first conductive structure located in the optical waveguide structure, wherein the first conductive structure is electrically connected to the photosensitive structure.

[0020] Optionally, the isolation structure includes a first isolation layer located in the first part and a second isolation layer located in the second part, and the materials of the first isolation layer and the second isolation layer are the same; the method for forming the reflective layer and the isolation structure includes: forming an initial isolation structure in the isolation groove; etching back the initial isolation structure until the second part is exposed, forming a first isolation layer in the first part; forming a reflective layer on the side wall of the second part; forming a second isolation layer in the second part, and the second isolation layer is located on the surface of the reflective layer.

[0021] Optionally, the method for forming the reflective layer includes: forming an initial reflective layer in the second part; removing the initial reflective layer in the middle area of ​​the second part until the surface of the first isolation layer is exposed, and forming a reflective layer on the side wall of the second part.

[0022] Optionally, it also includes: forming a second conductive structure in the optical waveguide structure, the second conductive structure is located on the first conductive structure and is electrically connected to the first conductive structure; when the material of the second conductive structure is the same as the material of the reflective layer, the second conductive structure is formed simultaneously with the initial reflective layer.

[0023] Optionally, the method for forming the second conductive structure and the initial reflective layer includes: forming a groove in the optical waveguide structure, the groove exposing the top surface of the first conductive structure; forming a reflective material layer in the groove, in the second part and on the optical waveguide structure; flattening the reflective material layer until the surface of the optical waveguide structure is exposed, forming the second conductive structure in the groove, and forming the initial reflective layer in the second part.

[0024] Optionally, the photosensitive structure includes a first doping region and a second doping region located on the first doping region, the conductivity type of the first doping region and the conductivity type of the second doping region are opposite to each other, and the surface of the substrate exposes the surface of the second doping region.

[0025] Optionally, before forming the optical waveguide structure on the substrate, the method further includes: forming a first protective layer on the substrate, wherein the material of the first protective layer is different from the material of the optical waveguide structure; and the first portion is located in the isolation region and in the first protective layer.

[0026] Correspondingly, the technical solution of the present invention also provides a method for forming an image sensor, including: providing a substrate, the substrate including a pixel area and a logic area, the pixel area including a photosensitive area and an isolation area surrounding the photosensitive area; forming a photosensitive structure in the photosensitive area; forming an optical waveguide structure on the substrate; forming an isolation groove in the isolation area and in the optical waveguide structure, the isolation groove surrounding the photosensitive area, the isolation groove including a first part and a second part located on the first part, the second part is located in the optical waveguide structure, and the first part is located in the isolation area; forming a reflective layer on the side wall of the second part and forming an isolation structure in the isolation groove, the isolation structure is also located on the surface of the reflective layer, the refractive index of the reflective layer material is less than the refractive index of the isolation structure material; forming a filter structure on the pixel area; forming a lens structure on the filter structure.

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

[0028] In the photoelectric sensor of the technical solution of the present invention, an isolation groove is formed in the isolation area and in the optical waveguide structure, the side wall of the second part of the isolation groove has a reflective layer, the isolation structure is also located on the surface of the reflective layer, and the refractive index of the reflective layer material is smaller than the refractive index of the isolation structure material, so that when light enters the reflective layer with a lower refractive index from the isolation structure with a higher refractive index, when the incident angle of the incident light is greater than a certain critical angle, the incident light will be totally reflected, so that the photons entering the isolation structure can be totally reflected at the interface between the isolation structure and the reflective layer and return to the corresponding photosensitive area, which can increase the number of photons entering the photosensitive area, so that the area of ​​the isolation area can be converted into an effective photosensitive area, thereby increasing the effective photosensitive area of ​​the entire photoelectric sensor, improving the photon detection efficiency (PDE), and improving the suppression of optical crosstalk between adjacent photosensitive areas.

[0029] Furthermore, the second part is located in the optical waveguide structure, and the refractive index of the reflective layer material is smaller than the refractive index of the optical waveguide structure material. Thus, when light enters the reflective layer with a lower refractive index from the optical waveguide structure with a higher refractive index, it can be totally reflected at the interface between the optical waveguide structure and the reflective layer and return to the corresponding photosensitive area, thereby reducing optical crosstalk between adjacent photosensitive areas.

[0030] Furthermore, when the material of the second conductive structure is the same as that of the reflective layer, the second conductive structure and the initial reflective layer can be formed simultaneously, thereby simplifying the process steps, improving production efficiency and saving costs.

[0031] Furthermore, the reflective layer is located on the second part of the side wall surface of the optical waveguide structure, and the height of the reflective layer is the same as the thickness of the optical waveguide structure. The thickness of the optical waveguide structure is thicker, and the height of the reflective layer is correspondingly higher, so that as much incident light entering the isolation structure as possible can be totally reflected at the interface between the isolation structure and the reflective layer and return to the corresponding photosensitive area, thereby increasing the number of photons entering the photosensitive area. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the structure of a photoelectric sensor in one embodiment;

[0033] Figures 2 to 9 is a structural schematic diagram of a photoelectric sensor forming process according to an embodiment of the present invention;

[0034] Fig.10 Schematic diagram of the structure of the image sensor in the embodiment of the present invention. DETAILED DESCRIPTION

[0035] As described in the background art, it is necessary to improve the photon detection efficiency of the photoelectric sensor. Now, an analysis and description will be given in conjunction with specific embodiments.

[0036] Figure 1 Schematic diagram of the structure of a photoelectric sensor in one embodiment.

[0037] Please refer to Figure 1 The photoelectric sensor includes: a substrate 100; the substrate 100 includes a photosensitive area I and an isolation area II surrounding the photosensitive area I; a photosensitive structure 101 located in the photosensitive area I; an isolation structure 102 located in the isolation area II, the isolation structure 102 surrounding the photosensitive area I; an optical waveguide structure located on the substrate 200, the optical waveguide structure includes several layers of first dielectric layers 103 and second dielectric layers 104 located on adjacent first dielectric layers 103, the refractive index of the first dielectric layer 103 material and the second dielectric layer 104 material are different.

[0038] In the image sensor, in order to avoid light signal crosstalk between the photosensitive areas I, the distance between the isolation areas II between the photosensitive areas I is widened or an isolation structure 102 is used in the isolation area II for isolation. The isolation structure 102 can improve the effect of preventing crosstalk, but it will occupy the effective photosensitive area. In addition, for optical isolation considerations, the inside of the isolation structure 102 is usually filled with silicon oxide with a refractive index lower than that of the substrate silicon, so that when the incident light R1 is incident from the photosensitive area I to the surface of the isolation structure 102, the incident light R1 is easy to be totally reflected, and most of the incident photons can be confined to the corresponding photosensitive area I. However, for the incident light R2 incident into the isolation structure 102, light crosstalk is still easy to occur between adjacent photosensitive areas I.

[0039] In order to solve the above problems, the technical solution of the present invention provides a photoelectric sensor and a method for forming the same, an image sensor and a method for forming the same, wherein an isolation groove is formed in an isolation area and in an optical waveguide structure, the side wall of the second part of the isolation groove has a reflective layer, the isolation structure is also located on the surface of the reflective layer, and the refractive index of the reflective layer material is less than the refractive index of the isolation structure material, so that when light enters the reflective layer from the isolation structure with a higher refractive index, when the incident angle of the incident light is greater than a certain critical angle, the incident light will be totally reflected, so that the photons entering the isolation structure can be totally reflected at the interface between the isolation structure and the reflective layer and return to the corresponding photosensitive area, which can increase the number of photons entering the photosensitive area, so that the area of ​​the isolation area can be converted into an effective photosensitive area, thereby increasing the effective photosensitive area of ​​the entire photoelectric sensor, improving the photon detection efficiency (PDE), and improving the suppression of optical crosstalk between adjacent photosensitive areas.

[0040] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] Figures 2 to 9Schematic diagram of the structure of the photoelectric sensor forming process in an embodiment of the present invention.

[0042] Please refer to Figure 2 , providing a substrate 200, wherein the substrate 200 includes a photosensitive region I and an isolation region II surrounding the photosensitive region I.

[0043] There are multiple photosensitive regions I and isolation regions II, which are arranged in an array. In this embodiment, a photosensitive region I and an isolation region II surrounding the photosensitive region I are schematically shown.

[0044] In this embodiment, the width of the photosensitive region I ranges from 2 micrometers to 15 micrometers; the width of the isolation region II ranges from 20 nanometers to 150 nanometers.

[0045] In this embodiment, the material of the substrate 200 is silicon.

[0046] In other embodiments, the substrate material includes silicon carbide, silicon germanium, a multinary semiconductor material composed of group III-V elements, silicon on insulator (SOI) or germanium on insulator (GOI). Among them, the multinary semiconductor material composed of group III-V elements includes InP, GaAs, GaP, InAs, InSb, InGaAs or InGaAsP.

[0047] Please continue to refer to Figure 2 , a photosensitive structure is formed in the photosensitive area I.

[0048] The photosensitive structure includes a first doping region 202 and a second doping region 203 located on the first doping region 202 . The conductivity type of the first doping region 202 and the conductivity type of the second doping region 203 are opposite to each other. The surface of the substrate 200 exposes the surface of the second doping region 203 .

[0049] The method for forming the photosensitive structure includes: performing a first ion implantation in the photosensitive region I to form a first doped region 202 in the photosensitive region I; performing a second ion implantation in the photosensitive region I on the first doped region 202 to form a second doped region 203 in the photosensitive region I on the first doped region 202, and the surface of the substrate 200 exposes the surface of the second doped region 203.

[0050] The conductivity type of the first doping region 202 includes N type or P type; the conductivity type of the second doping region 203 includes N type or P type.

[0051] In this embodiment, the depth of the first doping region 202 is in the range of 1 micrometer to 8 micrometers; the depth of the second doping region 203 is in the range of 1 micrometer to 8 micrometers.

[0052] In this embodiment, the width of the second doping region 203 is greater than that of the first doping region 202 , so that when the first conductive structure is subsequently formed on the photosensitive structure, it is easy to align and contact with the second doping region 203 .

[0053] In other embodiments, the width of the second doping region may be the same as the width of the first doping region, or the width of the second doping region may be smaller than the width of the first doping region.

[0054] In this embodiment, after the photosensitive structure is formed, the method further includes: forming a first protective layer 204 on the substrate 200. The first protective layer 204 is used to protect the surface of the photosensitive structure.

[0055] In this embodiment, the thickness of the first protective layer 204 is relatively thin, and the thickness of the first protective layer 204 is much smaller than the thickness of the optical waveguide structure formed subsequently, so as to avoid process waste.

[0056] The process of forming the first protection layer 204 includes: a chemical vapor deposition process, a physical vapor deposition process or an atomic layer deposition process.

[0057] The material of the first protection layer 204 includes a dielectric material, and the dielectric material includes one or more combinations of silicon oxide, silicon nitride, silicon carbide, silicon oxycarbide, silicon oxynitride, aluminum oxide, aluminum nitride, silicon carbide nitride, and silicon carbide nitride.

[0058] In this embodiment, the material of the first protection layer 204 includes silicon oxide. The silicon oxide material has a simple formation process and is easy to prepare.

[0059] Please refer to Figure 3 A light waveguide structure 206 is formed on the first protective layer 204, and a first conductive structure 205 is formed inside the light waveguide structure 206 and inside the first protective layer 204. The material of the light waveguide structure 206 is different from that of the first protective layer 204. The first conductive structure 205 is electrically connected to the photosensitive structure.

[0060] The method for forming the first conductive structure 205 and the optical waveguide structure 206 includes: forming an initial optical waveguide structure (not shown) on the first protective layer 204; forming a groove (not shown) in the initial optical waveguide structure and in the first protective layer 204, wherein the groove exposes a portion of the surface of the second doped region 203; forming a conductive material layer (not shown) in the groove and on the initial optical waveguide structure; planarizing the conductive material layer until the surface of the initial optical waveguide structure is exposed, and forming the first conductive structure 205 in the groove; after forming the first conductive structure 205, forming an optical waveguide material layer on the first conductive structure 205 and the initial optical waveguide structure, wherein the optical waveguide material layer and the initial optical waveguide structure constitute the optical waveguide structure 206.

[0061] In this embodiment, the thickness of the first protection layer 204 is smaller than the thickness of the optical waveguide structure 206 .

[0062] In this embodiment, the material of the optical waveguide structure 206 includes silicon nitride.

[0063] In this embodiment, the first conductive structure 205 is in contact and electrically connected with the second doped region 203 .

[0064] In this embodiment, part of the first conductive structure 205 is located in the second doping region 203 to ensure that the first conductive structure 205 is in full contact with the second doping region 203 to ensure good conductive function.

[0065] In this embodiment, the first conductive structure 205 is located at the edge of the photosensitive region I, close to the isolation region II, so as to reduce the situation where the first conductive structure 205 blocks the photosensitive region I and affects the photosensitivity efficiency.

[0066] In this embodiment, the material of the first conductive structure 205 includes metal or metal nitride; the metal includes: a combination of one or more of copper, aluminum, tungsten, cobalt, nickel and tantalum; the metal nitride includes a combination of one or more of tantalum nitride and titanium nitride.

[0067] Please refer to Figure 4 An isolation groove is formed in the optical waveguide structure 206 and the isolation region II, the isolation groove surrounds the photosensitive region I, the isolation groove includes a first portion 220 and a second portion 221 located on the first portion 220, and the second portion 221 is connected to the first portion 220.

[0068] In this embodiment, the second portion 221 is located in the optical waveguide structure 206 , and the first portion 220 is located in the isolation region II and in the first protection layer 204 .

[0069] In this embodiment, the isolation trench is located at a depth within the isolation region II to better isolate the photosensitive region I and reduce the optical crosstalk between adjacent photosensitive regions I.

[0070] In this embodiment, the depth of the isolation groove in the isolation region II is greater than or equal to 2 micrometers, so as to ensure that the isolation structure formed subsequently has a good isolation effect without wasting too much process.

[0071] The formation process of the isolation groove includes: forming a patterned photoresist layer (not shown) on the optical waveguide structure 206, wherein the patterned photoresist layer exposes the surface of the optical waveguide structure 206 on the isolation region II; etching the optical waveguide structure 206, the first protective layer 204 and the isolation region II using the patterned photoresist layer as a mask to form an isolation groove in the optical waveguide structure 206 and the isolation region II.

[0072] Next, a reflective layer is formed on the sidewall of the second portion 221 and an isolation structure is formed in the isolation groove. The isolation structure is also located on the surface of the reflective layer. The refractive index of the reflective layer material is less than the refractive index of the isolation structure material. Please refer to the formation process of the reflective layer and the isolation structure. Figures 5 to 8 .

[0073] Please refer to Figure 5 , forming an initial isolation structure 208 in the isolation trench.

[0074] The material of the initial isolation structure 208 includes silicon nitride, silicon oxide or polysilicon.

[0075] In this embodiment, the material of the initial isolation structure 208 includes silicon nitride. The silicon nitride material has a simple formation process and is easy to obtain.

[0076] The formation process of the initial isolation structure 208 includes: forming an isolation material layer (not shown) in the isolation groove and on the optical waveguide structure 206; planarizing the isolation material layer until the surface of the optical waveguide structure 206 is exposed, and forming the initial isolation structure 208 in the isolation groove.

[0077] Please refer to Figure 6 , the initial isolation structure 208 is etched back until the second portion 221 is exposed, and a first isolation layer 209 is formed in the first portion 220 .

[0078] The process of back-etching the initial isolation structure 208 includes a dry etching process. The material of the initial isolation structure 208 is different from that of the optical waveguide structure 206. Therefore, the etching rate of the initial isolation structure 208 by the dry etching process is greater than the etching rate of the optical waveguide structure 206, so as to avoid the process of back-etching the initial isolation structure 208 causing greater damage to the optical waveguide structure 206; in addition, the dry etching process can easily control the etching depth of the initial isolation structure 208, so that the second part located in the optical waveguide structure 206 can be completely exposed, and the dry etching process can easily make the formed first isolation layer 209 have a relatively flat surface, so that the subsequently formed reflective layer and the isolation structure have a relatively clear interface, which is conducive to the reflection of the incident light entering the reflective structure.

[0079] Please refer to Figure 6 and 7 , an initial reflective layer 213 is formed in the second portion 221 ; and a second conductive structure 212 is formed in the optical waveguide structure 206 , wherein the second conductive structure 212 is located on the first conductive structure 205 and is electrically connected to the first conductive structure 205 .

[0080] The refractive index of the material of the initial reflective layer 213 is smaller than the refractive index of the material of the optical waveguide structure 206 .

[0081] The material of the initial reflective layer 213 includes aluminum, copper, silver, gold, tungsten, magnesium oxide or aluminum oxide.

[0082] In this embodiment, the material of the initial reflective layer 213 includes aluminum.

[0083] In this embodiment, the material of the second conductive structure 212 is the same as that of the initial reflective layer 213, and the second conductive structure 212 and the initial reflective layer 213 are formed simultaneously. The second conductive structure 212 and the initial reflective layer 213 are formed simultaneously, thereby simplifying the process steps, improving production efficiency, and saving costs.

[0084] The method for forming the initial reflective layer 213 and the second conductive structure 212 includes: forming a groove 211 ( Figure 6 As shown in the figure), the groove 211 exposes the top surface of the first conductive structure 205; a reflective material layer (not shown) is formed in the groove 211, in the second portion 221 and on the optical waveguide structure 206; the reflective material layer is flattened until the surface of the optical waveguide structure 206 is exposed, a second conductive structure 212 is formed in the groove 211, and an initial reflective layer 213 is formed in the second portion 221.

[0085] The initial reflective layer 213 fills the second portion 221 so that the reflective layer formed by subsequent etching of the initial reflective layer 213 can be located on the complete sidewall surface of the second portion 221, increasing the reflective interface where the incident light entering the isolation structure is reflected on the reflective layer surface.

[0086] In this embodiment, the formation process of the reflective material layer includes an electroplating process or an evaporation process.

[0087] In other embodiments, the process for forming the reflective material layer includes a chemical vapor deposition process or a physical vapor deposition process.

[0088] In this embodiment, the second conductive structure 212 is electrically connected to the first conductive structure 205, and is used to connect the photosensitive structure to an external circuit; the second conductive structure 212 and the first conductive structure 205 are located in the edge area of ​​the photosensitive area I, close to the isolation area II, so as to weaken the shielding effect of the second conductive structure 212 and the first conductive structure 205 on the photosensitive area I, and reduce the situation in which the photosensitivity efficiency is affected by the shielding of the photosensitive area I by the second conductive structure 212 and the first conductive structure 205.

[0089] In other embodiments, the material of the second conductive structure is different from that of the initial reflective layer, and the second conductive structure and the initial reflective layer are formed in different steps.

[0090] The method for forming the initial reflective layer includes: depositing a reflective material layer (not shown) in the second portion and on the optical waveguide structure; etching back the reflective material layer until the surface of the optical waveguide structure is exposed, and forming the initial reflective layer in the second portion. The method for forming the second conductive structure includes: forming a groove (not shown) in the optical waveguide structure, the groove exposing the top surface of the first conductive structure; forming a conductive material layer in the groove; flattening the conductive material layer until the surface of the optical waveguide structure is exposed, and forming a second conductive structure in the groove.

[0091] Please refer to Figure 8 , remove the initial reflective layer 213 in the middle area of ​​the second part 221 until the surface of the first isolation layer 209 is exposed, and form a reflective layer 214 on the side wall of the second part 221; form a second isolation layer 215 in the second part 221, and the second isolation layer 215 is located on the surface of the reflective layer 214.

[0092] The isolation structure includes a first isolation layer 209 located in the first portion 220 and a second isolation layer 215 located in the second portion 221 .

[0093] The method for removing the initial reflective layer 213 in the middle area of ​​the second part 221 includes: forming a patterned mask layer (not shown) on the initial reflective layer 213, the patterned mask layer exposing the initial reflective layer 213 in the middle area of ​​the second part 221; using the patterned mask layer as a mask to remove the initial reflective layer 213 in the middle area of ​​the second part 221 until the surface of the first isolation layer 209 is exposed, and forming a reflective layer 214 on the side wall of the second part 221.

[0094] The reflective layer 214 is located on the side wall surface of the second portion 221 in the optical waveguide structure 206. The height of the reflective layer 214 is the same as the thickness of the optical waveguide structure 206. The thickness of the optical waveguide structure 206 is thicker, and correspondingly the height of the reflective layer 214 is higher, so that as much incident light entering the isolation structure as possible can be totally reflected at the interface between the isolation structure and the reflective layer 214 and return to the corresponding photosensitive area I, thereby increasing the number of photons entering the photosensitive area I.

[0095] In this embodiment, the process of removing the initial reflective layer 213 in the middle area of ​​the second part 221 using the patterned mask layer as a mask includes a dry etching process. The dry etching process can make the formed reflective layer 214 have a relatively smooth surface so that the incident light subsequently entering the isolation structure can be reflected on the surface of the reflective layer, reducing the occurrence of diffuse reflection.

[0096] In this embodiment, the thickness of the reflective layer 214 on the sidewall surface of the second portion 221 is less than half the width of the isolation trench, that is, space for forming a second isolation layer is reserved between the reflective layers 214 .

[0097] In this embodiment, the width of the isolation trench is the same as the width of the isolation region II. In other embodiments, the width of the isolation trench may also be smaller than the width of the isolation region.

[0098] The method for forming the second isolation layer 215 in the second portion 221 includes: forming an isolation material layer (not shown) in the second portion 221, on the top surface of the reflective layer 214 and on the surface of the optical waveguide structure 206; flattening the isolation material layer until the surface of the optical waveguide structure 206 and the surface of the reflective layer 214 are exposed, and forming the second isolation layer 215 in the second portion 221, wherein the second isolation layer 215 is located on the surface of the reflective layer 214.

[0099] In this embodiment, the first isolation layer 209 and the second isolation layer 215 are made of the same material, so as to avoid the situation where the light path of the light is changed at the interface between the first isolation layer 209 and the second isolation layer 215 when the first isolation layer 209 and the second isolation layer 215 are made of different materials.

[0100] The material of the second isolation layer 215 includes silicon nitride, silicon oxide or polysilicon.

[0101] In this embodiment, the material of the second isolation layer 215 includes silicon nitride.

[0102] Please continue to refer to Figure 8 , further comprising: forming a second protective layer 216 on the surface of the optical waveguide structure 206 , the surface of the isolation structure, and the top surface of the reflective layer 214 , for protecting the surface of the optical waveguide structure 206 , the surface of the isolation structure, and the top surface of the reflective layer 214 .

[0103] In this embodiment, the material of the second protective layer 216 includes silicon oxide, and the transmittance of the material of the second protective layer 216 is greater than 90% to allow light to pass through.

[0104] Please refer to Fig. 9 , Fig. 9 It is a schematic diagram of the optical path of light in the isolation structure. In this embodiment, the refractive index of the reflective layer 214 material is smaller than the refractive index of the isolation structure material, so that when the incident light R1 enters the reflective layer 214 with a lower refractive index from the isolation structure with a higher refractive index, when the incident angle of the incident light is greater than a certain critical angle, the incident light will be totally reflected, so that the photons entering the isolation structure can be totally reflected at the interface between the isolation structure and the reflective layer 214 and return to the corresponding photosensitive area I, which can increase the number of photons entering the photosensitive area I, so that the area of ​​the isolation area II can be converted into an effective photosensitive area, thereby increasing the overall effective photosensitive area of ​​the photoelectric sensor, improving the photon detection efficiency (PDE), and improving the suppression of optical crosstalk between adjacent photosensitive areas.

[0105] Please continue to refer to Fig. 9 The second part 221 is located in the optical waveguide structure 206, and the refractive index of the material of the reflective layer 214 is smaller than the refractive index of the material of the optical waveguide structure 206. Therefore, when the incident light R2 enters the reflective layer 214 with a lower refractive index from the optical waveguide structure 206 with a higher refractive index, it can be totally reflected at the interface between the optical waveguide structure 206 and the reflective layer 214 and return to the corresponding photosensitive area I, thereby reducing the optical crosstalk between adjacent photosensitive areas I.

[0106] Accordingly, the embodiment of the present invention further provides a photoelectric sensor, please continue to refer to Figure 8 ,include:

[0107] A substrate 200, wherein the substrate 200 includes a photosensitive region I and an isolation region II surrounding the photosensitive region I;

[0108] A photosensitive structure located in the photosensitive area I;

[0109] An optical waveguide structure 206 located on the substrate 200;

[0110] An isolation trench located in the isolation region II and the optical waveguide structure 206, the isolation trench surrounds the photosensitive region I, the isolation trench includes a first portion and a second portion located on the first portion, the second portion is located in the optical waveguide structure 206, and the first portion is located in the isolation region II;

[0111] A reflective layer 214 located on the sidewall of the second portion;

[0112] The isolation structure is located in the isolation trench, and the isolation structure is also located on the surface of the reflective layer 214. The refractive index of the material of the reflective layer 214 is smaller than the refractive index of the isolation structure material.

[0113] In this embodiment, the refractive index of the material of the reflective layer 214 is smaller than the refractive index of the material of the optical waveguide structure 206 .

[0114] In this embodiment, the material of the reflective layer 214 includes aluminum, copper, silver, gold, tungsten, magnesium oxide or aluminum oxide.

[0115] In this embodiment, the isolation structure includes a first isolation layer 209 located in the first part and a second isolation layer 215 located in the second part. The first isolation layer 209 and the second isolation layer 215 are made of the same material. The material of the isolation structure includes silicon nitride, silicon oxide or polysilicon.

[0116] In this embodiment, the depth of the isolation trench in the isolation region II is greater than the depth of the photosensitive structure.

[0117] In this embodiment, the photosensitive structure includes a first doping region 202 and a second doping region 203 located on the first doping region 202 , the conductivity type of the first doping region 202 and the conductivity type of the second doping region 203 are opposite to each other, and the surface of the substrate 200 exposes the surface of the second doping region 203 .

[0118] In this embodiment, the conductivity type of the first doping region 202 includes N type or P type; the conductivity type of the second doping region 203 includes N type or P type.

[0119] In this embodiment, the photoelectric sensor also includes: a first conductive structure 205 located in the optical waveguide structure 206 and in the first protective layer 204, the first conductive structure 205 being electrically connected to the photosensitive structure; and a second conductive structure 212 located in the optical waveguide structure 206, the second conductive structure 212 being located on the first conductive structure 205 and being electrically connected to the first conductive structure 205.

[0120] Correspondingly, an embodiment of the present invention also provides a method for forming an image sensor.

[0121] exist Figure 8 Please refer to the basis Fig.10 , the method for forming the image sensor comprises:

[0122] Providing a substrate 200, wherein the substrate 200 includes a pixel region and a logic region, wherein the pixel region includes a photosensitive region I and an isolation region II surrounding the photosensitive region I;

[0123] forming a photosensitive structure in the photosensitive area I;

[0124] forming an optical waveguide structure 206 on the substrate 200;

[0125] An isolation groove is formed in the isolation region II and the optical waveguide structure 206, the isolation groove surrounds the photosensitive region I, the isolation groove includes a first portion and a second portion located on the first portion, the second portion is located in the optical waveguide structure 206, and the first portion is located in the isolation region II;

[0126] Forming a reflective layer 214 on the sidewall of the second portion and forming an isolation structure in the isolation trench, wherein the isolation structure is also located on the surface of the reflective layer 214, and the refractive index of the reflective layer 214 material is smaller than the refractive index of the isolation structure material;

[0127] forming a light filtering structure 310 on the pixel region;

[0128] A lens structure 311 is formed on the filter structure 310 .

[0129] In this embodiment, the filter structure 310 includes a plurality of filter layers, and each pixel region has one filter layer; the filter layer is a red filter layer, a green filter layer or a blue filter layer.

[0130] In this embodiment, the material of the lens structure 311 includes silicone, polymethyl methacrylate (PMMA), polycarbonate (PC) or glass. The lens structure 311 is used to focus the incident light so that more incident light enters the photosensitive area I.

[0131] Accordingly, the embodiment of the present invention further provides a structure of an image sensor, please continue to refer to Fig.10 ,include:

[0132] A substrate 200, wherein the substrate 200 includes a pixel region and a logic region, wherein the pixel region includes a photosensitive region I and an isolation region II surrounding the photosensitive region I;

[0133] A photosensitive structure located in the photosensitive area I;

[0134] An optical waveguide structure 206 located on the substrate 200;

[0135] An isolation trench located in the isolation region II and the optical waveguide structure 206, the isolation trench surrounds the photosensitive region I, the isolation trench includes a first portion and a second portion located on the first portion, the second portion is located in the optical waveguide structure 206, and the first portion is located in the isolation region II;

[0136] A reflective layer 214 located on the sidewall of the second portion;

[0137] An isolation structure located in the isolation trench, the isolation structure is also located on the surface of the reflective layer 214, and the refractive index of the material of the reflective layer 214 is smaller than the refractive index of the material of the isolation structure;

[0138] A light filtering structure 310 located on the pixel area;

[0139] The lens structure 311 is located on the light filtering structure 310 .

[0140] 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, the substrate comprising a photosensitive region and an isolation region surrounding the photosensitive region; Photosensitive structures located within the photosensitive area; an optical waveguide structure located on a substrate; An isolation trench located in the isolation region and in the optical waveguide structure, the isolation trench surrounds the photosensitive region, the isolation trench includes a first portion and a second portion located on the first portion, the second portion is located in the optical waveguide structure, and the first portion is located in the isolation region; a reflective layer located on a side wall of the second portion; The isolation structure is located in the isolation trench, and the isolation structure is also located on the surface of the reflective layer. The refractive index of the reflective layer material is smaller than the refractive index of the isolation structure material.

2. The photoelectric sensor according to claim 1, characterized in that The refractive index of the reflective layer material is smaller than the refractive index of the optical waveguide structure material.

3. The photoelectric sensor according to claim 2, characterized in that The material of the reflective layer includes aluminum, copper, silver, gold, tungsten, magnesium oxide or aluminum oxide.

4. The photoelectric sensor according to claim 1, wherein: The isolation structure comprises a first isolation layer located in the first part and a second isolation layer located in the second part, the first isolation layer and the second isolation layer are made of the same material; the material of the isolation structure comprises silicon nitride, silicon oxide or polysilicon.

5. The photoelectric sensor according to claim 1, wherein: The depth of the isolation trench in the isolation region is greater than the depth of the photosensitive structure.

6. The photoelectric sensor according to claim 1, wherein: The photosensitive structure includes a first doping region and a second doping region located on the first doping region, the conductivity type of the first doping region and the conductivity type of the second doping region are opposite to each other, and the surface of the substrate exposes the surface of the second doping region.

7. The photoelectric sensor according to claim 6, characterized in that The conductivity type of the first doping region includes N type or P type; the conductivity type of the second doping region includes N type or P type.

8. The photoelectric sensor according to claim 1, wherein: Also includes: A first conductive structure located in the optical waveguide structure, wherein the first conductive structure is electrically connected to the photosensitive structure; A second conductive structure is located in the optical waveguide structure, wherein the second conductive structure is located on the first conductive structure and is electrically connected to the first conductive structure.

9. The photoelectric sensor according to claim 1, wherein: Also includes: A first protective layer is located on the substrate, the optical waveguide structure is located on the first protective layer, and the material of the first protective layer is different from that of the optical waveguide structure; the first portion is located in the isolation region and in the first protective layer.

10. An image sensor, characterized in that: include: A substrate, the substrate comprising a pixel area and a logic area, the pixel area comprising a photosensitive area and an isolation area surrounding the photosensitive area; Photosensitive structures located within the photosensitive area; an optical waveguide structure located on a substrate; An isolation trench located in the isolation region and in the optical waveguide structure, the isolation trench surrounds the photosensitive region, the isolation trench includes a first portion and a second portion located on the first portion, the second portion is located in the optical waveguide structure, and the first portion is located in the isolation region; a reflective layer located on a side wall of the second portion; An isolation structure located in the isolation trench, the isolation structure is also located on the surface of the reflective layer, and the refractive index of the reflective layer material is smaller than the refractive index of the isolation structure material; A light filtering structure located on the pixel area; A lens structure is located on the filter structure.

11. A method for forming a photoelectric sensor, characterized in that: include: Providing a substrate, the substrate comprising a photosensitive region and an isolation region surrounding the photosensitive region; forming a photosensitive structure in the photosensitive area; forming an optical waveguide structure on a substrate; forming an isolation trench in the optical waveguide structure and in the isolation region, the isolation trench surrounding the photosensitive region, the isolation trench comprising a first portion and a second portion located on the first portion, the second portion being located in the optical waveguide structure, and the first portion being located in the isolation region; A reflective layer is formed on the sidewall of the second portion and an isolation structure is formed in the isolation trench. The isolation structure is also located on the surface of the reflective layer. The refractive index of the reflective layer material is smaller than the refractive index of the isolation structure material.

12. The method for forming a photoelectric sensor according to claim 11, wherein: The refractive index of the reflective layer material is smaller than the refractive index of the optical waveguide structure material.

13. The method for forming a photoelectric sensor according to claim 12, wherein: Before forming the isolation grooves in the optical waveguide structure and in the isolation region, the method further includes: forming a first conductive structure located in the optical waveguide structure, wherein the first conductive structure is electrically connected to the photosensitive structure.

14. The method for forming a photoelectric sensor according to claim 13, wherein: The isolation structure comprises a first isolation layer located in the first part and a second isolation layer located in the second part, and the first isolation layer and the second isolation layer are made of the same material; The method for forming the reflective layer and the isolation structure includes: forming an initial isolation structure in the isolation groove; etching back the initial isolation structure until the second part is exposed, forming a first isolation layer in the first part; forming a reflective layer on the side wall of the second part; forming a second isolation layer in the second part, and the second isolation layer is located on the surface of the reflective layer.

15. The method for forming a photoelectric sensor according to claim 14, wherein: The method for forming the reflective layer comprises: forming an initial reflective layer in the second part; removing the initial reflective layer in the middle area of ​​the second part until the surface of the first isolation layer is exposed, and forming a reflective layer on the side wall of the second part.

16. The method for forming a photoelectric sensor according to claim 15, wherein: Also includes: forming a second conductive structure in the optical waveguide structure, wherein the second conductive structure is located on the first conductive structure and is electrically connected to the first conductive structure; When the material of the second conductive structure is the same as that of the reflective layer, the second conductive structure and the initial reflective layer are formed simultaneously.

17. The method for forming a photoelectric sensor according to claim 16, wherein: The method for forming the second conductive structure and the initial reflective layer includes: forming a groove in the optical waveguide structure, wherein the groove exposes the top surface of the first conductive structure; forming a reflective material layer in the groove, in the second part and on the optical waveguide structure; flattening the reflective material layer until the surface of the optical waveguide structure is exposed, forming the second conductive structure in the groove, and forming the initial reflective layer in the second part.

18. The method for forming a photoelectric sensor according to claim 11, wherein: The photosensitive structure includes a first doping region and a second doping region located on the first doping region, the conductivity type of the first doping region and the conductivity type of the second doping region are opposite to each other, and the surface of the substrate exposes the surface of the second doping region.

19. The method for forming a photoelectric sensor according to claim 11, wherein: Before forming the optical waveguide structure on the substrate, the method further includes: forming a first protective layer on the substrate, wherein the material of the first protective layer is different from the material of the optical waveguide structure; and the first portion is located in the isolation region and in the first protective layer.

20. A method for forming an image sensor, characterized in that: include: Providing a substrate, the substrate comprising a pixel area and a logic area, the pixel area comprising a photosensitive area and an isolation area surrounding the photosensitive area; forming a photosensitive structure in the photosensitive area; forming an optical waveguide structure on a substrate; forming an isolation trench in the isolation region and in the optical waveguide structure, the isolation trench surrounding the photosensitive region, the isolation trench comprising a first portion and a second portion located on the first portion, the second portion being located in the optical waveguide structure, and the first portion being located in the isolation region; Forming a reflective layer on the sidewall of the second portion and forming an isolation structure in the isolation trench, wherein the isolation structure is also located on the surface of the reflective layer, and the refractive index of the reflective layer material is smaller than the refractive index of the isolation structure material; forming a light filtering structure on the pixel region; A lens structure is formed on the filter structure.

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