CN118866920A - Imaging system, image sensor and method for manufacturing the same - Google Patents

Abstract

The embodiments of the present disclosure relate to the semiconductor field and provide an imaging system, an image sensor and a method for preparing the same, comprising: a substrate comprising a plurality of pixel units and an isolation structure for 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 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 side wall 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.

Description

Imaging system, image sensor and method for manufacturing the same

Technical Field

The embodiments of the present disclosure relate to the semiconductor field, and in particular to an imaging system, an image sensor, and a method for manufacturing the same.

Background Art

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

There is no obstruction from additional layers (e.g., metal layers) in the BSI image sensor. When light is incident on the back of the CMOS image sensor, it can be directed to the photodiode through a direct path, which is beneficial to increase the conversion of photons to 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 pixels of the pixel, the pixel will also generate electrons, which may cause crosstalk due to the detection of light by inappropriate photosensitive units. The 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 a preparation method thereof.

Summary of the invention

According to some embodiments of the present disclosure, an image sensor is provided on one hand, including:

A substrate, comprising a plurality of pixel units and an isolation structure separating the plurality of pixel units;

A plurality of color filters are located on the substrate and correspond to the plurality of pixel units respectively;

A grid structure, wherein the grid structure is located between the plurality of color filters and extends along a first direction and a second direction respectively, wherein the grid structure comprises a first grid layer and a second grid layer, wherein the second grid layer covers the side wall 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.

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.

In some embodiments, the first grid layer also 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 sidewall of the first oxide layer and the top and sidewall of the second oxide layer.

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.

In some embodiments, the thickness of the nitride layer is 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.

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

In some embodiments, 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.

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

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.

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.

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

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

forming a grid structure, wherein the grid structure is formed on the substrate and extends in a first direction and a second direction respectively, the grid structure comprises a first grid layer and a second grid layer, the second grid layer covers the sidewall 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;

A plurality of color filters are formed, wherein the color filters are formed on the substrate and correspond to the plurality of pixel units respectively, and the grid structure is located between the plurality of color filters.

In some embodiments, the step of forming a grid structure includes: stacking and depositing a first oxide layer, a conductive layer, and a second oxide layer in sequence on the substrate, and 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 the top of the first grid layer, and the first grid layer and the second grid layer constitute the grid structure.

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.

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.

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;

A camera comprises a lens and the image sensor or the image sensor prepared by the preparation method.

According to an embodiment of the present disclosure, the grid structure includes a first grid layer and a second grid layer, the second grid layer covers the side wall and the top of the first grid layer, and 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

One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings, and these exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise specified, 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 are 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 creative work.

FIG. 1 is a schematic top view of a partial structure of an image sensor in an embodiment of the present disclosure.

FIG. 2 is a circuit diagram of a pixel unit of an image sensor in an embodiment of the present disclosure.

3(a)-3(b) are cross-sectional views of the image sensor in the embodiment of the present disclosure along the A-A’ direction in FIG1 .

FIG. 4 is a schematic flow chart of a method for preparing an image sensor.

5 to 11 are schematic diagrams of cross-sectional structures along the A-A’ direction in FIG. 1 corresponding to each step of an image sensor manufacturing method provided in an embodiment of the present disclosure.

FIG. 12 is a schematic diagram of an imaging system provided in an embodiment of the present disclosure.

DETAILED DESCRIPTION

The following will describe the various embodiments of the present disclosure in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present disclosure, many technical details are provided in order to enable the reader to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can be implemented.

CMOS image sensors may include multiple additional layers formed on top of a substrate, such as dielectric layers and interconnect metal layers, wherein the interconnect metal layers are used to connect pixel units to peripheral circuits. The side of a CMOS image sensor with additional layers is generally referred to as the front side, while the side of the substrate opposite to the front side is referred to as the back side. Depending on the light path, CMOS image sensors can be further divided into two main categories, namely, front side illumination (FSI) image sensors and back side illumination (BSI) image sensors. In FSI image sensors, microlenses and color filters are arranged on the front side of the substrate, and light is incident on the photosensitive unit from the front side through the microlenses and color filters. Compared with FSI image sensors, microlenses and color filters in BSI image sensors are arranged on the back side of the substrate. The array of photosensitive units is arranged in the substrate and is sensitive to light incident through the back side of the substrate. Since there is no metal to block the incident light, the photosensitive unit can receive more light, thereby improving the optical sensitivity of the image sensor.

One challenge of BSI image sensors is optical crosstalk between adjacent pixel units. As the size of BSI image sensors becomes smaller, the distance between adjacent pixel units decreases, which in turn increases the possibility of optical crosstalk.

In order to solve the above problems, the embodiment of the present disclosure provides an image sensor, and the image sensor provided by the embodiment of the present disclosure will be described below in conjunction with the accompanying drawings. Figure 1 is a top view of a partial structure of the image sensor in the embodiment of the present disclosure; Figure 2 is a circuit schematic diagram of a pixel unit of the image sensor in the embodiment of the present disclosure; Figures 3(a)-3(b) are cross-sectional views of the image sensor in the embodiment of the present disclosure along the A-A’ direction in Figure 1.

1 to 3 , an image sensor 10 provided by 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;

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

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 side wall and the top of the first grid layer 106, wherein the refractive index of the second grid layer 107 is greater than the refractive index of the first grid layer 106. The details will be described below in conjunction with the accompanying drawings.

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 may be a silicon-on-insulator (SOI) substrate or a silicon substrate or may be made of materials such as silicon germanium, indium antimonide, lead telluride, indium arsenide, indium phosphide, gallium arsenide or gallium antimonide.

2, each 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 a charge 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 charge to the floating diffusion area FD. The floating diffusion area FD is a region that converts the charge into a voltage and can accumulatively store the charge 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, for example, a transfer signal TX. The transfer transistor TG may transfer the charge 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 charge 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 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 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.

1 , a plurality of pixel units 102 may be arranged in an array in a substrate 101 along a first direction X and a second direction Y. In some embodiments, taking a 3×3 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 disposed on the substrate 101, that is, the second grid structure 107 extends along the first direction X and the second direction Y, the plurality of pixel units 102 are disposed between the grid structures GD that intersect each other, and the grid structure GD is also disposed around the plurality of pixel units 102 arrays.

Continuing to refer to FIGS. 3( a)-3( b ), an isolation structure 103 is further disposed between the plurality of pixel units 102 . Exemplarily, 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 a 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, for example, silicon oxide (SiO ₂ ), hafnium oxide (HfO ₂ ), tantalum oxide (Ta ₂ O ₅ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ) 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, the first dielectric layer 104 may be aluminum oxide (Al ₂ O ₃ ), and the second dielectric layer 105 may be (SiO ₂ ). Alternatively, the isolation structure 103 may be a three-layer or multi-layer stacked structure, that is, it may include the first dielectric layer 104 and the second dielectric layer 105, and other dielectric layers may also be provided. For example, the first dielectric layer 104 may be aluminum oxide (Al ₂ O _{3 )} . ), the second dielectric layer 105 may be (SiO ₂ ), other dielectric layers may include tantalum oxide (Ta ₂ O ₅ ), or based on the above embodiment, an air gap may 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 may also extend to the surface of the substrate 101.

A plurality of color filters 108 are disposed 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 other colors. Exemplarily, the color filter may also be arranged in a Bayer pattern or any other suitable pattern. A microlens 109 may also be disposed above the color filter 108, and the microlens 109 may be semi-elliptical to guide the light incident on the color filter 108 to the corresponding pixel unit 102. Among them, 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.

In some embodiments, a protective layer 110 is further provided on the microlens 109. The protective layer 110 can be arranged on the upper surface of the microlens 109 in a random manner, for example, it can be arranged as a hemispherical curved surface, so as to protect the microlens 109 and cooperate 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 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.

Referring to Figures 2 and 3(a)-3(b), the grid structure GD is located between the 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 wall and the top of the first grid layer 106, wherein 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, and the light is reflected back to the corresponding pixel unit, so that the light deviates from other pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units.

In some embodiments, referring to FIG. 3( a ), the first grid layer 106 may be a stacked multilayer 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, and the second grid layer 107 covers the conductive layer 1063 and the sidewalls of the first oxide layer 1062, and 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, and the material of the conductive layer 1063 may be tungsten, titanium, or tantalum, wherein the first oxide layer 1062 and the second oxide layer 1064 may be used to improve the interface contact performance between the conductive layer 1063 and the second grid layer 107 or the second dielectric layer 105.

In some embodiments, the refractive index of the first oxide layer 1062 and the second oxide layer 1064 may both be smaller than the refractive index of the conductive layer 1063, and the refractive index of the conductive layer is 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 may 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 may both be silicon oxide with a refractive index of approximately 1.45, and the conductive layer 1063 may be tungsten with a refractive index of approximately 1.91.

In some embodiments, the top surface of the second grid layer 107 is less than the top surface height of the color filter 108 and the material of the second grid layer 107 may be a nitrogen-containing compound, for example, silicon nitride, with a refractive index of about 2.0. Therefore, when light is incident from the color filter 108 to the second grid layer 107, total reflection may occur at the interface between the second grid layer 107 and the first grid layer 106, and the light may be reflected back to the corresponding pixel unit, so that the light deviates from other pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units.

In some embodiments, the thickness of the first oxide layer 1062, the conductive layer 1063, and the second oxide layer 1064 may increase in sequence in a direction away from the substrate 101, that is, 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. Exemplarily, 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. Such a configuration may improve the structural stability of the first grid layer 106.

In other embodiments, referring to FIG. 3( b ), the first grid layer 106 may further include a nitride layer 1061, a first oxide layer 1062, a conductive layer 1063, and a second oxide layer 1064 are sequentially stacked on the nitride layer 1061, and the second grid layer 107 covers the nitride layer 1061, the conductive layer 1063, and the sidewalls of the first oxide layer 1062, and the top and sidewalls of the second oxide layer 1064. Since the nitride layer 106 has high hardness and strength, and a low thermal expansion coefficient, the substrate 101 and the first dielectric layer 104 and the second dielectric layer 105 can be effectively prevented from warping by disposing the nitride layer 1061 at the bottom of the first grid layer 106, thereby helping to improve the product yield of the image sensor 10.

In some embodiments, the material of the nitride layer 1061 and the second grid layer 107 may be the same, for example, both may be nitrogen-containing materials, such as silicon nitride and silicon carbide nitride. The refractive index of the nitride layer 1061 is equal to the refractive index of the second grid layer 107. Exemplarily, when the material of the nitride layer 1061 and the second grid layer 107 is both silicon carbide nitride, the refractive index is about 2.0.

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. Exemplarily, 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 configuration 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.

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.

FIG4 is a flow chart of the steps of a method for preparing an image sensor provided by one embodiment of the present disclosure, and FIGS. 5 to 11 are schematic structural diagrams along the A-A’ direction in FIG1 corresponding to each step in a method for preparing an image sensor provided by another embodiment of the present disclosure. The method for preparing the image sensor provided by the present embodiment will be described in detail below in conjunction with the accompanying drawings, and the parts that are the same or corresponding to the above-mentioned embodiments will not be described in detail below.

Step S100 : providing a substrate 101 , in which a plurality of pixel units 102 and an isolation structure 103 for separating the plurality of pixel units 102 are formed.

In some embodiments, referring to FIG5 , the substrate 101 may be a semiconductor material of other elements 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, the substrate 101 may be a silicon substrate doped with an N-type dopant such as phosphorus or arsenic.

2 , each 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 selection transistor SEL. Light is converted into an electrical signal by the photoelectric conversion layer PD, wherein the incident light may be visible light, for example, infrared light (IR), ultraviolet light (UV), X-rays, microwaves, other suitable types of light, or a combination thereof.

Ions are implanted into the substrate 101 to form a pixel unit 102. The pixel unit 102 includes a photoelectric conversion layer PD, which can convert an optical signal into an electrical signal, and the pixel unit 102 is in contact with the substrate 101. In this embodiment, the type of ions implanted into the substrate 101 for forming the pixel unit 102 is not limited, and the required photoelectric conversion layer PD, transfer transistor TG, floating diffusion region FD, reset transistor RST, source follower transistor SF and selection transistor SEL devices can be formed. Exemplarily, if the substrate 101 is P-type doped, N-type ions are implanted into the substrate 101, and the implanted ions can specifically be ions with five valence electrons, such as phosphorus ions or arsenic ions. When the phosphorus ions replace silicon atoms, a negatively charged electron is provided to the valence band of the crystal, thereby forming a pixel unit 102 of an N-type photodiode. In other embodiments, when the substrate 101 is N-type doped, P-type ions can also be implanted into the substrate 101 to form a pixel unit 102 of a P-type photodiode. In the process of forming the pixel unit 102 , in order to ensure the yield of the pixel unit 102 formed after ion implantation, multiple ion implantations at different angles may be performed to form the pixel unit 102 conforming to a preset pattern.

The substrate 101 is etched to form a trench, and the first dielectric layer 104 and the second dielectric layer 105 are filled in the trench to form an isolation structure 130. The materials of the first dielectric layer 104 and the second dielectric layer 105 can both be silicon oxide or other high dielectric constant materials, such as silicon oxide (SiO ₂ ), hafnium oxide (HfO ₂ ), tantalum oxide (Ta ₂ O ₅ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ) 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 alternately performed to form a single-layer or multi-layer dielectric layer, and 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.

Step S200 forms a grid structure GD, which is formed on the substrate 101 and extends along the first direction X and the 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 side wall and the top of the first grid layer 106, wherein the refractive index of the second grid layer 107 is greater than the refractive index of the first grid layer 106.

In some embodiments, referring to Figures 6-10, a first oxide layer 1062, a conductive layer 1063, and a second oxide layer 1064 are stacked and deposited in sequence on a substrate 101. Exemplarily, the first oxide layer 1062, the conductive layer 1063, and the second oxide layer 1064 are stacked and deposited in sequence on a second dielectric layer 105 on the substrate 101. Exemplarily, the thickness of the first oxide layer 1062 can range from 150nm to 200nm, the thickness of the conductive layer can range from 200nm to 250nm, and the thickness of the second oxide layer 1064 can range from 300nm to 350nm, so as 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 a combination thereof, and the material of the conductive layer 1063 may be tungsten, titanium or tantalum, wherein the first oxide layer 1062 and the second oxide layer 1064 can be used to improve the interface contact performance between the conductive layer 1063 and the second grid layer 107 or the second dielectric layer 105.

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

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.

9-10, the second grid layer 107 is deposited on the first grid layer 106, and the second grid layer 107 is patterned. The remaining second grid layer 107 covers the sidewall and the top of the first grid layer 106, and the first grid layer 106 and the second grid layer 107 constitute a grid structure GD. The process of depositing the second grid layer 107 may include CVD, PVD, ALD or other deposition processes, and the thickness of the deposited second grid layer 107 may range from 10nm to 50nm. The top surface of the second grid layer 107 is less than the height of 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 about 2.0.

In some embodiments, the refractive index of the first oxide layer 1062 and the second oxide layer 1064 may be both smaller than the refractive index of the conductive layer 1063, and the refractive index of the conductive layer is 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 may also be equal and smaller than the refractive index of the conductive layer 1063, and illustratively, the materials of the first oxide layer 1062 and the second oxide layer 1064 may both be silicon oxide, with a refractive index of about 1.45, and the conductive layer 1063 may be tungsten, with a refractive index of about 1.91. Therefore, when light is incident from the color filter 108 to the second grid layer 107, total reflection may occur at the interface between the second grid layer 107 and the first grid layer 106, and the light may be reflected back to the corresponding pixel unit, so that the light deviates from other pixel units, thereby effectively avoiding optical crosstalk between adjacent pixel units.

In some embodiments, the width of the grid structure GD may 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 may 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 the adjacent pixel unit 102, further avoiding optical crosstalk.

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 , respectively. The grid structure GD is located between the plurality of color filters 108 .

In some embodiments, referring to FIG. 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 the 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"), which can be used to add pigments or dyes to form a color filter, 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 may be greater than the thickness of the grid structure GD, and the color filter 108 may cover the grid structure GD.

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 filter 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 repeated 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.

In some embodiments, a microlens 109 may be formed above the color filter 108, and 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 made of a transparent organic material or an inorganic compound material, for example, a transparent polymer material based on a polystyrene resin, a polyimide resin, a polysiloxane resin, an acrylic resin, an 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, and 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.

The present disclosure also provides an imaging system 50, with reference to FIG. 12, which uses the above-mentioned image sensor 10 to capture images. The imaging system 50 of FIG. 12 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 a microlens formed on an 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 a circuit for converting analog pixel data into corresponding digital image data to be provided to the storage and processing circuit 40. If desired, the camera module 30 may be provided with an array of lenses 20 and an array of corresponding image sensors 10.

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

In summary, the present disclosure provides an image sensor and a method for preparing 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, and the light is reflected 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.

Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present disclosure, and in practical applications, various changes can 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 can make various changes and modifications without departing from the spirit and scope of the embodiments of the present disclosure, so the protection scope of the embodiments of the present disclosure shall be based on the scope defined in the claims.

Claims (15)

1. An image sensor is provided, which is capable of detecting a light source, characterized by comprising the following steps:

a substrate including a plurality of pixel units and an isolation structure separating the plurality of pixel units;

A plurality of color filters on the substrate and corresponding to the plurality of pixel units, respectively;

and a grid structure located between the plurality of color filters and extending in a first direction and a second direction, respectively, the grid structure including a first grid layer and a second grid layer covering sidewalls and a top of the first grid layer, wherein a refractive index of the second grid layer is greater than a refractive index of the first grid layer.

2. The image sensor of claim 1, wherein the image sensor comprises a sensor array,

The first grid layer comprises a first oxide layer, a conductive layer and a second oxide layer which are stacked in sequence, and the second grid layer covers the conductive layer, the side wall of the first oxide layer and the top and the side wall of the second oxide layer.

3. The image sensor of claim 2, wherein the image sensor further comprises a sensor element,

The first grid layer further comprises a nitride layer, the first oxide layer, the conductive layer and the second oxide layer are sequentially stacked on the nitride layer, and the second grid layer covers the nitride layer, the conductive layer, the side wall of the first oxide layer, and the top and the side wall of the second oxide layer.

4. The image sensor of claim 3, wherein the image sensor comprises a sensor array,

The thicknesses of the first oxide layer, the conductive layer and the second oxide layer are sequentially increased along the direction away from the substrate.

5. The image sensor of claim 4, wherein the sensor further comprises a sensor element,

The thickness of the nitride layer is 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.

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

7. The image sensor of claim 6, wherein the first oxide layer and the second oxide layer each have a refractive index that is less than a refractive index of the conductive layer, and wherein the conductive layer has a refractive index that is less than a refractive index of the second grid layer.

8. The image sensor of claim 7, wherein the refractive index of the nitride layer is equal to the refractive index of the second grid layer.

9. The image sensor of claim 1, wherein the image sensor comprises a sensor array,

The 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.

10. The image sensor of claim 1, wherein the image sensor comprises a sensor array,

The isolation structure comprises a first dielectric layer and a second dielectric layer, wherein the first dielectric layer and the second dielectric layer are filled in the isolation structure and extend to the upper surface of the substrate.

11. A method of manufacturing an image sensor, comprising:

providing a substrate, wherein a plurality of pixel units and an isolation structure for separating the pixel units are formed in the substrate;

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 comprises a first grid layer and a second grid layer, the second grid layer covers the side wall and the top of the first grid layer, and the refractive index of the second grid layer is larger than that of the first grid layer;

And forming a plurality of color filters, wherein the color filters are formed on the substrate and respectively correspond to the pixel units, and the grid structure is positioned among the color filters.

12. The method of manufacturing an image sensor of claim 11, wherein the step of forming a grid structure comprises: sequentially stacking and depositing a first oxide layer, a conductive layer and a second oxide layer on the substrate, and patterning the first oxide layer, the conductive layer and the second oxide layer to form the first grid layer;

And 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 side wall and the top of the first grid layer, wherein the first grid layer and the second grid layer form the grid structure.

13. The method for manufacturing an image sensor according to claim 12, wherein,

Depositing a nitride layer prior to depositing the first oxide layer on the substrate;

the nitride layer, the first oxide layer, the conductive layer, and the second oxide layer are patterned to form the first grid layer.

14. The method of manufacturing an image sensor of claim 11, wherein the step of forming a plurality of color filters comprises:

A layer of color filter material is deposited over the substrate and the grid structure, the layer of color filter material being patterned to form a plurality of the color filters spaced apart by the grid structure.

15. An imaging system, comprising:

A processor and a memory;

A camera comprising a lens and the image sensor prepared by the image sensor of any one of claims 1-10 or the method of preparation of any one of claims 11-14.