Imaging system, image sensor and preparation method thereof

Abstract

The embodiments of the present disclosure relate to the field of semiconductors and provide an imaging system, an image sensor, and a method for manufacturing the same, including: a substrate comprising a plurality of pixel units and an isolation structure separating the plurality of pixel units; a plurality of color filters located on the substrate and corresponding to the plurality of pixel units, respectively; a grid structure located between the color filters and extending in a first direction and a second direction, respectively, the grid structure comprising a first grid layer and a second grid layer, the second grid layer covering the sidewalls and top of the first grid layer, wherein the refractive index of the second grid layer is greater than the refractive index of the first grid layer.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductors, and in particular to an imaging system, an image sensor, and a method for manufacturing the same. Background Art

[0002] Image sensors are semiconductor devices that convert optical information into electrical signals. For example, they can convert the variable attenuation of light waves into signals (i.e., small bursts of current that convey information). Such image sensors include charge-coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors. Based on differences in the optical path, CMOS image sensors can be further divided into front-side illuminated (FSI) image sensors and back-side illuminated (BSI) image sensors.

[0003] In BSI image sensors, there are no obstructions caused by additional layers (e.g., metal layers). Light incident on the back of the CMOS image sensor can be directed directly to the photodiode, which helps increase the conversion of photons into electrons. However, as the pixel unit in the image sensor decreases, light may be detected by adjacent or neighboring photosensitive units. That is, when light is incident on the adjacent pixel of the pixel, the pixel will also generate electrons. This causes crosstalk due to the detection of light by inappropriate photosensitive units. Crosstalk may reduce the performance of the image sensor, increase noise, and reduce the signal generated by the image sensor. Therefore, it is necessary to propose a new image sensor and its preparation method. Summary of the Invention

[0004] According to some embodiments of the present disclosure, an image sensor is provided, including:

[0005] A substrate comprising a plurality of pixel units and an isolation structure separating the plurality of pixel units;

[0006] a plurality of color filters, located on the substrate and corresponding to the plurality of pixel units respectively;

[0007] A grid structure is located between the plurality of color filters and extends along a first direction and a second direction respectively, the grid structure includes a first grid layer and a second grid layer, the second grid layer covers the sidewalls and the top of the first grid layer, wherein the refractive index of the second grid layer is greater than the refractive index of the first grid layer.

[0008] In some embodiments, the first grid layer includes a first oxide layer, a conductive layer, and a second oxide layer stacked in sequence, and the second grid layer covers the conductive layer and sidewalls of the first oxide layer and the top and sidewalls of the second oxide layer.

[0009] In some embodiments, the first grid layer further includes a nitride layer, the first oxide layer, the conductive layer and the second oxide layer are stacked sequentially on the nitride layer, and the second grid layer covers the nitride layer, the conductive layer, the sidewalls of the first oxide layer and the top and sidewalls of the second oxide layer.

[0010] In some embodiments, the thicknesses of the first oxide layer, the conductive layer, and the second oxide layer increase sequentially along a direction away from the substrate.

[0011] In some embodiments, the thickness of the nitride layer is greater than the thickness of the first oxide layer and smaller than the thickness of the conductive layer and the thickness of the second oxide layer.

[0012] In some embodiments, the refractive index of the first oxide layer is equal to the refractive index of the second oxide layer.

[0013] In some embodiments, the refractive index of the first oxide layer and the second oxide layer is smaller than the refractive index of the conductive layer, and the refractive index of the conductive layer is smaller than the refractive index of the second grid layer.

[0014] In some embodiments, the refractive index of the nitride layer is equal to the refractive index of the second grid layer.

[0015] In some embodiments, a material of the second grid layer includes a nitrogen-containing compound, and a top surface of the second grid layer is flush with a top surface of the color filter.

[0016] In some embodiments, the isolation structure includes a first dielectric layer and a second dielectric layer, wherein the first dielectric layer and the second dielectric layer fill the isolation structure and extend to the upper surface of the substrate.

[0017] According to some embodiments of the present disclosure, another aspect of the present disclosure further provides a method for manufacturing an image sensor, including:

[0018] Providing a substrate, wherein a plurality of pixel units and an isolation structure separating the plurality of pixel units are formed in the substrate;

[0019] forming a grid structure, wherein the grid structure is formed on the substrate and extends along a first direction and a second direction respectively, the grid structure comprising a first grid layer and a second grid layer, the second grid layer covering the sidewalls and the top of the first grid layer, wherein the refractive index of the second grid layer is greater than the refractive index of the first grid layer;

[0020] A plurality of color filters are formed on the substrate and correspond to the plurality of pixel units respectively. The grid structure is located between the plurality of color filters.

[0021] In some embodiments, the steps of forming a grid structure include: stacking and depositing a first oxide layer, a conductive layer, and a second oxide layer in sequence on the substrate, patterning the first oxide layer, the conductive layer, and the second oxide layer to form the first grid layer; depositing a second grid material layer on the substrate and the first grid layer, and removing the second grid material layer on the substrate to form the second grid layer covering the sidewalls and top of the first grid layer, the first grid layer and the second grid layer constituting the grid structure.

[0022] In some embodiments, before depositing the first oxide layer on the substrate, the method further includes depositing a nitride layer; and patterning the nitride layer, the first oxide layer, the conductive layer, and the second oxide layer to form the first grid layer.

[0023] In some embodiments, a color filter material layer is deposited on the substrate and the grid structure, and the color filter material layer is patterned to form a plurality of the color filters separated by the grid structure.

[0024] According to some embodiments of the present disclosure, another aspect of the present disclosure further provides an imaging system, including: a processor and a memory;

[0025] A camera comprising a lens and the image sensor or the image sensor prepared by the preparation method.

[0026] According to an embodiment of the present disclosure, the grid structure includes a first grid layer and a second grid layer, and the second grid layer covers the side walls and top of the first grid layer. By setting the refractive index of the second grid layer to be greater than the refractive index of the first grid layer, light incident from the color filter to the second grid layer can be totally reflected at the interface between the second grid layer and the first grid layer, reflecting the light back to the corresponding pixel unit, causing the light to deviate from other adjacent pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the traditional technology, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Schematic top view of a partial structure of an image sensor in an embodiment of the present disclosure.

[0029] Figure 2 4 is a circuit schematic diagram of a pixel unit of an image sensor in an embodiment of the present disclosure.

[0030] Figure 3(a)-3(b) The image sensor in the embodiment of the present disclosure is along Figure 1 Cross-sectional view along the AA' direction.

[0031] Figure 4 A schematic flow chart of a method for preparing an image sensor is provided.

[0032] Figures 5 to 11 The corresponding edges of each step of the image sensor manufacturing method provided in the embodiment of the present disclosure are Figure 1 Schematic diagram of the cross-sectional structure along the A-A' direction.

[0033] Figure 12 A schematic diagram of an imaging system provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] The following describes various embodiments of the present disclosure in detail with reference to the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present disclosure to facilitate a better understanding of the present disclosure. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can still be implemented.

[0035] CMOS image sensors can include multiple additional layers formed on top of a substrate, such as dielectric layers and interconnect metal layers, which are used to connect pixel cells to peripheral circuitry. The side of a CMOS image sensor with the additional layers is typically called the front side, while the side of the substrate opposite the front side is called the back side. Based on the light path, CMOS image sensors can be further divided into two main categories: front-side illumination (FSI) image sensors and back-side illumination (BSI) image sensors. In FSI image sensors, microlenses and color filters are located on the front side of the substrate, and light from the front side passes through the microlenses and color filters to the photosensitive cells. Compared to FSI image sensors, the microlenses and color filters in BSI image sensors are located on the back side of the substrate. The photosensitive cell array is housed within the substrate and is sensitive to light incident through the back side of the substrate. Because there is no metal blocking the incident light, the photosensitive cells are able to receive more light, thereby improving the optical sensitivity of the image sensor.

[0036] One challenge with BSI image sensors is optical crosstalk between adjacent pixel cells. As BSI image sensors become smaller, the distance between adjacent pixel cells decreases, which in turn increases the likelihood of optical crosstalk.

[0037] To solve the above problems, an embodiment of the present disclosure provides an image sensor. The image sensor provided by the embodiment of the present disclosure will be described below with reference to the accompanying drawings. Figure 1 is a schematic top view of a partial structure of an image sensor in an embodiment of the present disclosure; Figure 2 is a circuit schematic diagram of a pixel unit of an image sensor in an embodiment of the present disclosure; Figure 3(a)-3(b) The image sensor in the embodiment of the present disclosure is along Figure 1 Cross-sectional view along the AA' direction.

[0038] refer to Figure 1 FIG3 , an image sensor 10 provided in an embodiment of the present disclosure includes: a substrate 101 including a plurality of pixel units 102 and an isolation structure 103 separating the plurality of pixel units 102 ;

[0039] A plurality of color filters 108 are located on the substrate 101 and correspond to the plurality of pixel units 102 respectively;

[0040] The grid structure 106 is located between the multiple color filters 108 and extends along the first direction X and the second direction Y respectively. The grid structure 106 includes a first grid layer 106 and a second grid layer 107. The second grid layer 107 covers the sidewalls and the top of the first grid layer 106. The refractive index of the second grid layer 107 is greater than the refractive index of the first grid layer 106. This will be described in detail below with reference to the accompanying drawings.

[0041] refer to Figure 3(a)-3(b) , a substrate 101 includes a plurality of pixel units 102 and an isolation structure 103 separating the plurality of pixel units 102, wherein the substrate 101 can be a silicon-on-insulator (SOI) or a silicon substrate or is made of materials such as silicon germanium, indium antimonide, lead telluride, indium arsenide, indium phosphide, gallium arsenide or gallium antimonide.

[0042] refer to Figure 2Each pixel unit 102 may include a photoelectric conversion layer PD, a transfer transistor TG, a floating diffusion area FD, a reset transistor RST, a source follower transistor SF, and a selection transistor SEL. The photoelectric conversion layer PD may generate charges proportional to the amount of light incident from the outside. The photoelectric conversion layer PD may be coupled to a transfer transistor TG that transfers the generated and accumulated charges to the floating diffusion area FD. The floating diffusion area FD is a region that converts charges into voltage and can accumulate charges due to its parasitic capacitance. One end of the transfer transistor TG may be connected to the photoelectric conversion layer PD, and the other end of the transfer transistor TG may be connected to the floating diffusion area FD. The transfer transistor TG may be a transistor driven by a predetermined bias voltage, for example, a transfer signal TX. The transfer transistor TG may transfer the charges generated by the photoelectric conversion layer PD to the floating diffusion area FD according to the transfer signal TX. The source follower transistor SF may amplify the potential change of the floating diffusion area FD that receives the charges from the photoelectric conversion layer PD, and may output the amplified change to the output line Vout. When the source follower transistor SF is turned on, a predetermined potential provided to the drain of the source follower transistor SF, for example, the power supply voltage VDD, can be transferred to the drain region of the selection transistor SEL. The selection transistor SEL can select the unit pixel to be read row by row. The selection transistor SEL can be a transistor driven by a selection line to which a predetermined bias voltage is applied, for example, a row selection signal RS. The reset transistor RST can periodically reset the floating diffusion area FD. The reset transistor RST can be driven by a reset line to which a predetermined bias voltage is applied, for example, a reset signal RX. When the reset transistor RST is turned on by the reset signal RX, a predetermined potential provided to the drain of the reset transistor RST, for example, the power supply voltage VDD, can be transferred to the floating diffusion area FD.

[0043] refer to Figure 1 , the plurality of pixel units 102 may be arranged in an array on the substrate 101 along a first direction X and a second direction Y. In some embodiments, taking a 3x3 array as an example, the plurality of pixel units 102 may include P1, P2, P3, P4, P5, P6, P7, P8, and P9 disposed between grid structures GD located on the substrate 101. That is, the second grid structure 107 extends along the first direction X and the second direction Y, and the plurality of pixel units 102 are located between the intersecting grid structures GD. The grid structure GD is also disposed around the array of the plurality of pixel units 102.

[0044] Continue to refer Figure 3(a)-3(b)An isolation structure 103 is also provided between the plurality of pixel units 102. For example, the isolation structure 103 may be a deep trench isolation (DTI), which may extend from the surface of the substrate 101 into the substrate to isolate adjacent pixel units 102. In some embodiments, the width of the isolation structure 103 may gradually decrease in the direction toward the substrate 101. The isolation structure 103 may be filled with a first dielectric layer 104 and a second dielectric layer 105, wherein the materials of the first dielectric layer 104 and the second dielectric layer 105 may both be silicon oxide or other high dielectric constant materials, such as silicon oxide (SiO2), hafnium oxide (HfO2), tantalum oxide (Ta2O5), titanium oxide (TiO2), zirconium oxide (ZrO2), aluminum oxide (Al2O3), and the like. In other embodiments, the isolation structure 103 may also be a single-layer structure, that is, it may only include the first dielectric layer 104 or the second dielectric layer 105. For example Typically, the first dielectric layer 104 can be aluminum oxide (Al2O3), the second dielectric layer 105 can be (SiO2), or a three-layer or multi-layer stacked structure can be included, that is, it can include the first dielectric layer 104 and the second dielectric layer 105, and other dielectric layers can also be provided. For example, the first dielectric layer 104 can be aluminum oxide (Al2O3), the second dielectric layer 105 can be (SiO2), and the other dielectric layer can include tantalum oxide (Ta2O5). Alternatively, based on the above embodiment, an air gap can be further provided in the second dielectric layer 105. The first dielectric layer 104 and the second dielectric layer 105 fill the isolation structure 103 and can also extend to the surface of the substrate 101.

[0045] A plurality of color filters 108 are located on the substrate 101 and are arranged corresponding to the plurality of pixel units 102. In some embodiments, the color filter 108 may include a red filter, a green filter, a blue filter, an infrared (IR) filter, a transparent filter, or a color filter of another color. Exemplarily, the color filters may also be arranged in a Bayer pattern or any other suitable pattern. A microlens 109 may also be provided above the color filter 108. The microlens 109 may be semi-elliptical to guide the light incident on the color filter 108 to the corresponding pixel unit 102. The microlens 109 may be an optically transparent material, for example, a transparent polymer material based on a polystyrene-based resin, a polyimide-based resin, a polysiloxane-based resin, an acrylic-based resin, an epoxy-based resin, or a copolymer resin thereof, or an inorganic material based on silicon oxide or silicon nitride.

[0046] In some embodiments, a protective layer 110 is further provided on the microlens 109. The protective layer 110 can be configured to conform to the upper surface of the microlens 109, for example, it can be configured as a hemispherical surface. This protects the microlens 109 while also cooperating with the microlens 109 to increase or decrease the focal length, thereby improving image resolution. For example, the material of the protective layer 110 can be an inorganic oxide layer, including but not limited to at least one or more of silicon oxide, titanium oxide, zirconium oxide, and hafnium oxide.

[0047] refer to Figure 2 and 3(a) -3(b), a grid structure GD, is located between multiple color filters 108 and extends along the first direction X and the second direction Y respectively. The grid structure GD can also be located around the color filter 108 array. The grid structure GD includes a first grid layer 106 and a second grid layer 107. The second grid layer 107 covers the side walls and the top of the first grid layer 106. The refractive index of the second grid layer 107 is greater than the refractive index of the first grid layer 106. By setting the refractive index of the second grid layer 107 to be greater than the refractive index of the first grid layer 106, the light incident from the color filter 108 to the second grid layer 107 can be totally reflected at the interface between the second grid layer 107 and the first grid layer 106, reflecting the light back to the corresponding pixel unit, causing the light to deviate from other pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units.

[0048] In some embodiments, referring to FIG. 3( a ), the first grid layer 106 may be a stacked multi-layer structure, wherein a first oxide layer 1062, a conductive layer 1063, and a second oxide layer 1064 are sequentially stacked in a direction perpendicular to the substrate 101. The second grid layer 107 covers the sidewalls of the conductive layer 1063 and the first oxide layer 1062, as well as the top and sidewalls of the second oxide layer 1064. Exemplarily, the materials of the first oxide layer 1062 and the second oxide layer 1063 may include, but are not limited to, at least one of silicon oxide, aluminum oxide, tantalum oxide, and combinations thereof. The material of the conductive layer 1063 may be tungsten, titanium, or tantalum. The first oxide layer 1062 and the second oxide layer 1064 may be used to improve the interfacial contact performance between the conductive layer 1063 and the second grid layer 107 or the second dielectric layer 105.

[0049] In some embodiments, the refractive index of the first oxide layer 1062 and the second oxide layer 1064 can both be smaller than the refractive index of the conductive layer 1063, and the refractive index of the conductive layer can be smaller than the refractive index of the second grid layer 107, wherein the refractive index of the first oxide layer 1062 and the refractive index of the second oxide layer 1064 can also be equal and both smaller than the refractive index of the conductive layer 1063. Exemplarily, the materials of the first oxide layer 1062 and the second oxide layer 1064 can both be silicon oxide with a refractive index of approximately 1.45, and the conductive layer 1063 can be tungsten with a refractive index of approximately 1.91.

[0050] In some embodiments, the top surface of the second grid layer 107 is lower than the top surface of the color filter 108, and the material of the second grid layer 107 may be a nitrogen-containing compound, such as silicon nitride, with a refractive index of approximately 2.0. Therefore, when light is incident on the second grid layer 107 from the color filter 108, total internal reflection occurs at the interface between the second grid layer 107 and the first grid layer 106, reflecting the light back to the corresponding pixel unit, deflecting the light away from other pixel units, thereby effectively preventing optical crosstalk between adjacent pixel units.

[0051] In some embodiments, the thicknesses of the first oxide layer 1062, the conductive layer 1063, and the second oxide layer 1064 may increase sequentially in a direction away from the substrate 101, i.e., the thickness of the conductive layer 1063 is greater than the thickness of the first oxide layer 1062 and less than the thickness of the second oxide layer 1064. For example, the thickness of the first oxide layer 1062 may range from 150 nm to 200 nm, the thickness of the conductive layer may range from 200 nm to 250 nm, and the thickness of the second oxide layer 1064 may range from 300 nm to 350 nm. This configuration can improve the structural stability of the first grid layer 106.

[0052] In other embodiments, referring to FIG3( b ), the first grid layer 106 may further include a nitride layer 1061, with a first oxide layer 1062, a conductive layer 1063, and a second oxide layer 1064 stacked sequentially on the nitride layer 1061. The second grid layer 107 covers the nitride layer 1061, the conductive layer 1063, and the sidewalls of the first oxide layer 1062, as well as the top and sidewalls of the second oxide layer 1064. Because the nitride layer 106 has high hardness and strength and a low thermal expansion coefficient, providing the nitride layer 1061 at the bottom of the first grid layer 106 can effectively prevent warping of the substrate 101 and the first and second dielectric layers 104 and 105, thereby helping to improve the product yield of the image sensor 10.

[0053] In some embodiments, the nitride layer 1061 and the second grid layer 107 can be made of the same material, for example, both can be nitrogen-containing materials, such as silicon nitride or silicon carbide nitride. The refractive index of the nitride layer 1061 is equal to the refractive index of the second grid layer 107. For example, when both the nitride layer 1061 and the second grid layer 107 are made of silicon carbide nitride, the refractive index is approximately 2.0.

[0054] In some embodiments, the thickness of the nitride layer 1061 can be greater than the thickness of the first oxide layer 1062 and less than the thickness of the conductive layer 1063 and the thickness of the second oxide layer 1064. For example, the thickness range of the nitride layer 1061 can be 100-150nm, the thickness range of the first oxide layer 1062 can be 20nm~50nm, the thickness range of the conductive layer can be 200nm~250nm, and the thickness range of the second oxide layer 1064 can be 300nm~350nm. Such a setting can effectively improve the structural stability of the first grid layer 106 while avoiding warping of the substrate 101 and the first dielectric layer 104 and the second dielectric layer 105.

[0055] Correspondingly, another embodiment of the present disclosure provides a method for preparing an image sensor, which can be used to form the above-mentioned image sensor.

[0056] Figure 4 A flowchart of a method for manufacturing an image sensor according to an embodiment of the present disclosure is provided. Figure 5-Figure 11 The corresponding edges of each step in the method for preparing an image sensor provided in another embodiment of the present disclosure are Figure 1 The structural diagram along the AA' direction in FIG. 1 is a structural diagram of the image sensor in FIG. 1 . The manufacturing method of the image sensor provided by this embodiment will be described in detail below in conjunction with the accompanying drawings. Parts identical or corresponding to the above embodiment will not be described in detail below.

[0057] In step S100 , a substrate 101 is provided. A plurality of pixel units 102 and an isolation structure 103 separating the plurality of pixel units 102 are formed in the substrate 101 .

[0058] In some embodiments, reference Figure 5 The substrate 101 may be a semiconductor material such as silicon-on-insulator (SOI), germanium, or diamond, or may be made of materials such as silicon germanium, indium antimonide, lead telluride, indium arsenide, indium phosphide, gallium arsenide, or gallium antimonide. The substrate 101 may also be a doped silicon substrate, for example, a silicon substrate doped with an N-type dopant such as phosphorus or arsenic.

[0059] refer to Figure 2Each pixel unit 102 may include a photoelectric conversion layer PD, a transfer transistor TG, a floating diffusion region FD, a reset transistor RST, a source follower transistor SF, and a select transistor SEL. Light is converted into an electrical signal by the photoelectric conversion layer PD. The incident light may be visible light, for example, infrared (IR), ultraviolet (UV), X-rays, microwaves, other suitable types of light, or a combination thereof.

[0060] Ion implantation is performed on substrate 101 to form pixel units 102. Pixel units 102 include a photoelectric conversion layer PD that converts optical signals into electrical signals. Pixel units 102 are in contact with substrate 101. In this embodiment, the type of ions implanted into substrate 101 to form pixel units 102 is not limited; the desired photoelectric conversion layer PD, transfer transistor TG, floating diffusion region FD, reset transistor RST, source follower transistor SF, and select transistor SEL devices can be formed. For example, if substrate 101 is P-type doped, N-type ions are implanted into substrate 101. The implanted ions can specifically be ions with five valence electrons, such as phosphorus ions or arsenic ions. When phosphorus ions replace silicon atoms, they contribute a negatively charged electron to the valence band of the crystal, thereby forming pixel units 102 that are N-type photodiodes. In other embodiments, if substrate 101 is N-type doped, P-type ions can also be implanted into substrate 101 to form pixel units 102 that are P-type photodiodes. During the process of forming the pixel units 102 , in order to ensure the yield of the pixel units 102 formed after ion implantation, multiple ion implantations at different angles may be performed to form the pixel units 102 conforming to a predetermined pattern.

[0061] The substrate 101 is etched to form a trench, and the trench is filled with a first dielectric layer 104 and a second dielectric layer 105 to form an isolation structure 130. The first dielectric layer 104 and the second dielectric layer 105 can both be made of silicon oxide or other high-k materials, such as silicon oxide (SiO2), hafnium oxide (HfO2), tantalum oxide (Ta2O5), titanium oxide (TiO2), zirconium oxide (ZrO2), aluminum oxide (Al2O3), and the like. The deposition process for filling the first dielectric layer 104 and the second dielectric layer 105 may include chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD) or other deposition processes, wherein the deposition processes of the first dielectric layer 104 and the second dielectric layer 105 may be repeated or alternated to form a single-layer or multi-layer dielectric layer. The first dielectric layer 104 and the second dielectric layer 105 fill the isolation structure 103 and may also extend to the surface of the substrate 101.

[0062] In step S200, a grid structure GD is formed on the substrate 101 and extends along a first direction X and a second direction Y, respectively. The grid structure GD includes a first grid layer 106 and a second grid layer 107. The second grid layer 107 covers the sidewalls and the top of the first grid layer 106. The refractive index of the second grid layer 107 is greater than the refractive index of the first grid layer 106.

[0063] In some embodiments, referring to FIG. Figure 10 A first oxide layer 1062, a conductive layer 1063, and a second oxide layer 1064 are sequentially deposited on the substrate 101. For example, the first oxide layer 1062, the conductive layer 1063, and the second oxide layer 1064 are sequentially deposited on the second dielectric layer 105 on the substrate 101. For example, the thickness of the first oxide layer 1062 may range from 150 nm to 200 nm, the thickness of the conductive layer may range from 200 nm to 250 nm, and the thickness of the second oxide layer 1064 may range from 300 nm to 350 nm to ensure the structural stability of the formed first grid layer 106. In some embodiments, the material of the first oxide layer 1062 and the second oxide layer 1063 may include, but is not limited to, at least one of silicon oxide, aluminum oxide, tantalum oxide, and combinations thereof. The material of the conductive layer 1063 may be tungsten, titanium, or tantalum. The first oxide layer 1062 and the second oxide layer 1064 may be used to improve the interfacial contact performance between the conductive layer 1063 and the second grid layer 107 or the second dielectric layer 105.

[0064] In other embodiments, before depositing the first oxide layer 1062 on the substrate 101, a nitride layer 1061 is further deposited. For example, the nitride layer 1061, the first oxide layer 1062, the conductive layer 1063, and the second oxide layer 1064 are sequentially stacked and deposited on the second dielectric layer 105 on the substrate 101. The nitride layer 1061 can be made of the same material as the second grid layer 107. For example, both can be nitrogen-containing materials, such as silicon nitride or silicon carbide nitride. The thickness of the deposited nitride layer 1061 can be greater than the thickness of the first oxide layer 1062 and less than the thickness of the conductive layer 1063 and the thickness of the second oxide layer 1064. For example, the thickness of the nitride layer 1061 can range from 100 to 150 nm, the thickness of the first oxide layer 1062 can range from 20 nm to 50 nm, the thickness of the conductive layer can range from 200 nm to 250 nm, and the thickness of the second oxide layer 1064 can range from 300 nm to 350 nm. This configuration can effectively improve the structural stability of the first grid layer 106 while preventing warping of the substrate 101 and the first and second dielectric layers 104 and 105. The deposition process of the nitride layer 1061, the first oxide layer 1062, the conductive layer 1063, and the second oxide layer 1064 can include electroplating, sputtering, CVD, PVD, or other deposition processes, wherein the CVD process can include PECVD, LPCVD, or ALD.

[0065] The stacked first oxide layer 1062, conductive layer 1063, and second oxide layer 1064 are patterned, or the stacked nitride layer 1061, first oxide layer 1062, conductive layer 1063, and second oxide layer 1064 are patterned to form the first grid layer 106. The etching process may be dry etching or wet etching.

[0066] refer to Figure 9-10 A second grid layer 107 is deposited on the first grid layer 106 and patterned. The remaining second grid layer 107 covers the sidewalls and top of the first grid layer 106. The first grid layer 106 and the second grid layer 107 form a grid structure GD. The deposition process of the second grid layer 107 may include CVD, PVD, ALD, or other deposition processes. The deposited second grid layer 107 may have a thickness ranging from 10 nm to 50 nm. The top surface of the second grid layer 107 is less than the height of the top surface of the color filter 108. The material of the second grid layer 107 may be a nitrogen-containing compound, such as silicon nitride, with a refractive index of approximately 2.0.

[0067] In some embodiments, the refractive index of the first oxide layer 1062 and the second oxide layer 1064 can both be lower than the refractive index of the conductive layer 1063, and the refractive index of the conductive layer can be lower than the refractive index of the second grid layer 107. The refractive index of the first oxide layer 1062 and the refractive index of the second oxide layer 1064 can also be equal and lower than the refractive index of the conductive layer 1063. For example, the materials of the first oxide layer 1062 and the second oxide layer 1064 can both be silicon oxide, with a refractive index of approximately 1.45, and the conductive layer 1063 can be tungsten, with a refractive index of approximately 1.91. Therefore, when light from the color filter 108 is incident on the second grid layer 107, total internal reflection can occur at the interface between the second grid layer 107 and the first grid layer 106, reflecting the light back to the corresponding pixel unit, deflecting the light away from other pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units.

[0068] In some embodiments, the width of the grid structure GD can be in the range of 20 nm to 300 nm, which is substantially equal to or greater than the width of the isolation structure 130, so as to cover the isolation structure 130. Therefore, the grid structure GD can effectively block nearly vertical incident light from propagating into the isolation structure 130, thereby refracting nearly vertical incident light transmitted into the isolation structure 130 to adjacent pixel units 102, further avoiding optical crosstalk.

[0069] S300 : Forming a plurality of color filters 108 . The color filters are formed on the substrate 101 and correspond to the plurality of pixel units 102 . The grid structure GD is located between the plurality of color filters 108 .

[0070] In some embodiments, reference Figure 11 After forming the grid structure GD, a color filter material layer is deposited on the substrate 101 and the grid structure GD, and the color filter material layer is patterned to form a plurality of color filters 108 separated by the grid structure GD. Exemplarily, the color filter 108 is formed on the second dielectric layer 105 between the grid structures GD, and each color filter 108 is correspondingly arranged on a corresponding pixel unit 102. The material of the color filter 108 may include, but is not limited to, a colored or dyed material, such as acrylic acid. For example, polymethyl methacrylate ("PMMA") or propylene glycol monostearate ("PGMS") can be used to add pigments or dyes to form a color filter, and can also include silicon oxide, silicon nitride or other suitable polymers, and can be formed by CVD, PVD, or a combination thereof. The thickness of the color filter 108 can be greater than the thickness of the grid structure GD, and the color filter 108 can cover the grid structure GD.

[0071] In some embodiments, the color filter 108 may include a red filter, a green filter, a blue filter, an infrared (IR) filter, a transparent filter, or a filter of another color. Exemplarily, the color filters may also be arranged in a Bayer pattern or any other suitable pattern. For example, the color filter 108 may include one or more of red (R), green (G), and blue (B) filters that transmit light in the red, green, and blue spectral ranges, and the R, G, and B type color filters 108 are arranged in a repeating RGB pattern in each pixel row of the image sensor 10. In addition, the color filter 108 may also be configured to have different types of color filters 108, such as red, green, blue, and infrared.

[0072] In some embodiments, a microlens 109 may be formed above the color filter 108. The microlens 109 may be semi-elliptical in shape to guide the light incident on the color filter 108 to the corresponding pixel unit 102. The microlens 109 may be made of a transparent organic material or an inorganic compound material, for example, a transparent polymer material based on polystyrene resin, polyimide resin, polysiloxane resin, acrylic resin, epoxy resin, or a copolymer resin thereof, or an inorganic material based on silicon oxide or silicon nitride. In some embodiments, a protective layer 110 may be formed on the microlens 109. The protective layer 110 may be formed on the upper surface of the microlens 109, for example, it may be set to a hemispherical curved surface, so as to protect the microlens 109 while cooperating with the microlens 109 to increase or decrease the focal length to improve the resolution of the image. Exemplarily, the material of the protective layer 110 may be an inorganic oxide layer, including but not limited to at least one or more of silicon oxide, titanium oxide, zirconium oxide, and hafnium oxide.

[0073] The present disclosure also provides an imaging system 50, referring to Figure 12 , the imaging system 50 captures images using the above-mentioned image sensor 10. Figure 12The imaging system 50 may be a portable electronic device such as a camera, a mobile phone, a tablet computer, a webcam, a video camera, a video surveillance system, an automotive imaging system, a video game system with imaging capabilities, or any other desired imaging system or device that captures digital image data. The camera module 30 may be used to convert incident light into digital image data. The camera module 30 may include a lens 20 and a corresponding image sensor 10. The lens 20 may include a fixed lens and / or an adjustable lens, and may include microlenses formed on the imaging surface of the image sensor 10. During an image capture operation, light from a scene may be focused onto the image sensor 10 through the lens 20. The image sensor 10 may include circuitry for converting analog pixel data into corresponding digital image data to be provided to the storage and processing circuitry 40. If desired, the camera module 30 may be provided with an array of lenses 20 and an array of corresponding image sensors 10.

[0074] The storage and processing circuitry 40 may include one or more integrated circuits, such as memory and processors (e.g., image processing circuitry, a microprocessor, storage devices such as random access memory and non-volatile memory, etc.), and may be implemented using components separate from and / or forming part of the camera module 30 (e.g., circuitry forming part of an integrated circuit that includes the image sensor 10 or within a module associated with the image sensor 10). Image data captured by the camera module 30 may be processed and stored using the processing circuitry 40 (e.g., using an image processing engine on the processing circuitry 40, using an imaging mode selection engine on the processing circuitry 40, etc.). The processed image data may be provided to an external device (e.g., a computer, an external display, or other device) as desired using wired and / or wireless communication paths coupled to the processing circuitry 40.

[0075] In summary, the present disclosure provides an image sensor and a method for manufacturing the same. By setting the refractive index of the second grid layer to be greater than the refractive index of the first grid layer, light incident from the color filter to the second grid layer can be totally reflected at the interface between the second grid layer and the first grid layer, reflecting the light back to the corresponding pixel unit, causing the light to deviate from other adjacent pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units.

[0076] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present disclosure, and in actual applications, various changes may be made to them in form and detail without departing from the spirit and scope of the embodiments of the present disclosure. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the embodiments of the present disclosure. Therefore, the scope of protection of the embodiments of the present disclosure shall be based on the scope defined in the claims.

Claims

1. An image sensor, characterized in that: include: A substrate comprising a plurality of pixel units and an isolation structure separating the plurality of pixel units; a plurality of color filters, located on the substrate and corresponding to the plurality of pixel units respectively; a grid structure, the grid structure being located between the plurality of color filters and extending in a first direction and a second direction, respectively, the grid structure comprising a first grid layer and a second grid layer, the first grid layer comprising a nitride layer, a first oxide layer, a conductive layer, and a second oxide layer stacked in sequence, the second grid layer covering the nitride layer, the conductive layer, and sidewalls of the first oxide layer, as well as the top and sidewalls of the second oxide layer, the thickness of the first oxide layer, the conductive layer, and the second oxide layer increasing in sequence in a direction away from the substrate; the thickness of the nitride layer being greater than the thickness of the first oxide layer and less than the thickness of the conductive layer and the thickness of the second oxide layer; The refractive index of the second grid layer is greater than the refractive index of the first grid layer.

2. The image sensor according to claim 1, wherein The refractive index of the first oxide layer is equal to the refractive index of the second oxide layer.

3. The image sensor according to claim 2, wherein: The refractive indexes of the first oxide layer and the second oxide layer are both smaller than the refractive index of the conductive layer, and the refractive index of the conductive layer is smaller than the refractive index of the second grid layer.

4. The image sensor according to claim 3, wherein: The refractive index of the nitride layer is equal to the refractive index of the second grid layer.

5. The image sensor according to claim 1, wherein A material of the second grid layer includes a nitrogen-containing compound, and a top surface of the second grid layer is smaller than a height of a top surface of the color filter.

6. The image sensor according to claim 1, wherein The isolation structure includes a first dielectric layer and a second dielectric layer, wherein the first dielectric layer and the second dielectric layer fill the isolation structure and extend to the upper surface of the substrate.

7. A method for preparing an image sensor, characterized in that: include: Providing a substrate, wherein a plurality of pixel units and an isolation structure separating the plurality of pixel units are formed in the substrate; Depositing a nitride layer, a first oxide layer, a conductive layer, and a second oxide layer in sequence on the substrate, and patterning the nitride layer, the first oxide layer, the conductive layer, and the second oxide layer to form a first grid layer; Depositing a second grid material layer on the substrate and the first grid layer, and removing the second grid material layer on the substrate to form a second grid layer covering the sidewalls and the top of the first grid layer, wherein the first grid layer and the second grid layer constitute a grid structure; The grid structure extends along a first direction and a second direction respectively, and the refractive index of the second grid layer is greater than the refractive index of the first grid layer; A plurality of color filters are formed on the substrate and correspond to the plurality of pixel units respectively. The grid structure is located between the plurality of color filters.

8. The method for preparing an image sensor according to claim 7, wherein: The steps of forming a plurality of color filters include: A color filter material layer is deposited on the substrate and the grid structure, and the color filter material layer is patterned to form a plurality of color filters separated by the grid structure.

9. An imaging system, characterized in that: include: processor and memory; A camera comprising a lens and the image sensor according to any one of claims 1 to 6 or the image sensor prepared by the preparation method according to any one of claims 7 to 8.

Images