Pixel structure for improving quantum efficiency of image sensor and manufacturing method thereof

Abstract

The application discloses a pixel structure and a manufacturing method for improving quantum efficiency of an image sensor, and relates to the field of image sensors, and solves the problem of reduced quantum efficiency of the image sensor caused by the entry of gap photons between on-chip microlenses of the image sensor, and comprises: a light filtering layer formed by a plurality of color filtering arrays; and a pixel structure layer comprising a first structure and a second structure, the bottom surfaces of the first structure and the second structure are flush, the highest point of the second structure is higher than or flush with the highest point of the first structure, the first structure is located between two adjacent color filtering arrays, the length of the bottom surface of the second structure is not less than the projection length of the gap, and the second structure is distributed at the gap positions of four corners of the color filtering array pixels; the gap is formed by adjacent on-chip microlenses of the image sensor. The application improves the quantum efficiency of the image sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of image sensors, and more particularly, to a pixel structure and a manufacturing method for improving quantum efficiency of an image sensor. BACKGROUND

[0002] The quantum efficiency of an image sensor is an important indicator for measuring the photoelectric conversion capability of the image sensor, and is directly related to the image output effect of the image sensor. Higher quantum efficiency means higher utilization rate of light signals by the sensor, which can more effectively collect light signals in low light environments. It is particularly important for high-contrast shooting scenes, as it can improve the detail presentation of both dark and bright parts in an image, significantly improve the dynamic range of the sensor, restore image detail, and improve color saturation.

[0003] For the pixel structure of existing image sensors, the gap between the on-chip microlenses is limited, and the absorption and reflection of light by the materials in each part of the pixel structure. Even with a backside illumination (BSI) pixel structure with a shorter optical path, 5% to 21% of the photons will pass through the gap between the on-chip microlenses into the pixel, some of which will be absorbed by the metal mesh, and the other part will enter the photodiode of the adjacent pixel after multiple reflections, causing optical crosstalk. The photons focused by the on-chip microlenses will be reflected when passing through the interface between each optical coating and the interface between the optical coating and the semiconductor substrate due to the sudden change in refractive index, reducing the light signal entering the semiconductor substrate and resulting in reduced quantum efficiency. SUMMARY

[0004] The purpose of the present application is to provide a pixel structure and a manufacturing method for improving the quantum efficiency of an image sensor, which solves the problem of reduced quantum efficiency of the image sensor caused by the entry of photons through the gap between the on-chip microlenses.

[0005] The above technical purpose of the present application is achieved by the following technical solutions:

[0006] In a first aspect of the present application, a pixel structure for improving the quantum efficiency of an image sensor is provided, which includes:

[0007] a light filtering layer formed by a plurality of color filtering arrays; and

[0008] The pixel structure layer includes a first structure and a second structure. The bottom surfaces of the first structure and the second structure are flush. The highest point of the second structure is higher than or flush with the highest point of the first structure. The first structure is located between two adjacent color filter arrays. The length of the bottom surface of the second structure is not less than the projected length of the gap. The second structure is distributed at the gap positions of the four corners of the color filter array pixels. The gap is formed by adjacent on-chip microlenses of the image sensor.

[0009] In one implementation, the side of the second structure faces the pixel center of the color filter array.

[0010] In one implementation, the angle formed by the side surface of the second structure and the vertical direction, and its height, satisfy the following relationship:

[0011] [tan(∠2α) * Hpyr]<( * Pitch) / 2, where Pitch represents the size of a single pixel, α represents the angle formed by each side of the second structure with the vertical direction, and Hpyr represents the height of the second structure.

[0012] A second aspect of the present invention provides an image sensor, comprising:

[0013] A semiconductor substrate, wherein a plurality of photodiode regions are disposed on the semiconductor substrate;

[0014] A dielectric layer having a first refractive index is located on the semiconductor substrate;

[0015] A high-n-value antireflective layer having a second refractive index, the high-n-value antireflective layer being located on the dielectric layer;

[0016] A transition layer having a third refractive index is located on the high n-value antireflective layer;

[0017] A passivation layer having a fourth refractive index is located on the transition layer;

[0018] A pixel structure for improving the quantum efficiency of an image sensor, as provided in the first aspect of the present invention, comprises: a filter layer formed by a plurality of color filter arrays; and a pixel structure layer comprising a first structure and a second structure, wherein the bottom surfaces of the first structure and the second structure are flush, the highest point of the second structure is higher than or flush with the highest point of the first structure, the first structure is located between two adjacent color filter arrays, the length of the bottom surface of the second structure is not less than the projected length of the gap, and the second structure is distributed at the gap positions at the four corners of the color filter array pixels; wherein the gap is formed by adjacent on-chip microlenses of the image sensor; and wherein the first structure and the second structure are at least partially embedded in the passivation layer.

[0019] A planarization layer, the planarization layer being located on the filter layer; and

[0020] A microlens assembly comprising an on-chip microlens having a fifth refractive index and a lens antireflection layer having a sixth refractive index, the microlens assembly being located on the planarization layer, and the lens antireflection layer being located on the on-chip microlens.

[0021] In one implementation, the first refractive index of the dielectric layer is less than the second refractive index of the high n-value antireflective layer.

[0022] A third aspect of the present invention provides a method for manufacturing an image sensor, the method comprising:

[0023] A semiconductor substrate is provided, wherein a plurality of photodiode regions are disposed thereon;

[0024] A dielectric layer having a first refractive index is formed on the semiconductor substrate;

[0025] A high-n-value anti-reflection layer with a second refractive index is formed above the dielectric layer;

[0026] A transition layer with a third refractive index is formed above the high n-value antireflective layer;

[0027] A passivation layer with a fourth refractive index is formed above the transition layer;

[0028] A pixel structure for improving the quantum efficiency of an image sensor, as provided in the first aspect of the invention, is formed above the passivation layer. The pixel structure includes: a filter layer formed by a plurality of color filter arrays; and a pixel structure layer including a first structure and a second structure, wherein the bottom surfaces of the first structure and the second structure are flush, the highest point of the second structure is higher than or flush with the highest point of the first structure, the first structure is located between two adjacent color filter arrays, the length of the bottom surface of the second structure is not less than the projected length of the gap, and the second structure is distributed at the gap positions at the four corners of the color filter array pixels; wherein the gap is formed by adjacent on-chip microlenses of the image sensor; and wherein the first structure and the second structure are at least partially embedded within the passivation layer.

[0029] A planarization layer is formed above the filter layer;

[0030] An on-sheet microlens with a fifth refractive index is formed above the planarization layer; and

[0031] An anti-reflective layer with a sixth refractive index is formed above the microlens on the sheet.

[0032] In one implementation, if the real part of the second refractive index of the high n-value antireflective layer is within a first range, the high n-value antireflective layer is formed according to a preset first thickness distribution function; wherein, the first thickness distribution function describes the distribution relationship between the thickness of the high n-value antireflective layer and the real part of the second refractive index.

[0033] In one implementation, if the real part of the second refractive index is within a second range, and the thickness of the high-n-value antireflective layer conforms to a first thickness distribution function, a passivation layer and a transition layer are formed according to a preset second thickness distribution function; wherein, the second thickness distribution function describes the distribution relationship between the thickness of the passivation layer and the thickness of the transition layer, and the second range is within the first range.

[0034] In one implementation, if the real part of the second refractive index is within a third range, and the thickness of the passivation layer and the thickness of the transition layer conform to a first thickness distribution function, the passivation layer and the transition layer are formed according to a preset third thickness distribution function; wherein, the third thickness distribution function describes the distribution relationship between the thickness of the passivation layer and the thickness of the transition layer, and the third range is within the first range.

[0035] In one implementation, if the real part of the second refractive index is within a fourth range, and the thickness of the passivation layer and the thickness of the transition layer conform to a first thickness distribution function, the passivation layer and the transition layer are formed according to a preset fourth thickness distribution function; wherein, the fourth thickness distribution function describes the distribution relationship between the thickness of the passivation layer and the thickness of the transition layer, and the fourth range is within the first range.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. In the pixel structure for improving the quantum efficiency of an image sensor provided by the present invention, the first structure located between two adjacent color filter arrays plays a role in isolating different colors and reducing crosstalk. When light leaks through the gap between the microlenses on the chip, the second structure can collect the photons leaking through the gap between the microlenses on the chip into the photodiode region through the side of the second structure, thereby reducing the reflectivity of the photons in the process of entering the semiconductor substrate, increasing the total amount of effective light signal entering the semiconductor substrate, and realizing the improvement of the quantum efficiency of the image sensor.

[0038] 2. In the method for fabricating an image sensor provided by the present invention, by optimizing the thickness of the high n-value anti-reflection layer, the transition layer and the passivation layer, the fabricated image sensor can achieve the effect of having the best anti-reflection capability, thereby maximizing the quantum efficiency of the image sensor. Attached Figure Description

[0039] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0040] Figure 1 A top view schematic diagram of a pixel structure for improving the quantum efficiency of an image sensor, provided as an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the horizontal cross-section of an image sensor provided in an embodiment of the present invention;

[0042] Figure 3 This is a structural schematic diagram of a diagonal cross-section of an image sensor provided in an embodiment of the present invention;

[0043] Figure 4 A schematic diagram of a mask for fabricating a pixel structure to improve the quantum efficiency of an image sensor, provided for an embodiment of the present invention;

[0044] Figure 5 A schematic diagram of the quantum efficiency distribution provided for an embodiment of the present invention;

[0045] Figure 6A graph showing the distribution relationship between the thickness of the high n-value antireflective layer and the real part of the second refractive index, provided in an embodiment of the present invention.

[0046] Figure 7 A first distribution diagram showing the relationship between the thickness of the passivation layer and the thickness of the transition layer is provided for an embodiment of the present invention;

[0047] Figure 8 A second distribution diagram showing the relationship between the thickness of the passivation layer and the thickness of the transition layer is provided for an embodiment of the present invention;

[0048] Figure 9 This is a third distribution diagram showing the relationship between the thickness of the passivation layer and the thickness of the transition layer, provided for an embodiment of the present invention.

[0049] Figure labels and figure descriptions:

[0050] 101. On-chip microlens; 102. Lens antireflection layer; 103. Planarization layer; 104. Color filter array; 105-1. First structure; 105-2. Second structure; 106. Passivation layer; 107. Transition layer; 108. High n-value antireflection layer; 109. Dielectric layer; 110. Semiconductor substrate; 111. Photodiode region. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0052] It should be noted that the terms "comprising" or "may include" used in the various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in the various embodiments of this application, the terms "comprising," "having," and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0053] It should be understood that terms such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0054] Quantum efficiency, a crucial indicator of an image sensor's photoelectric conversion capability, is directly related to its image output quality. Higher quantum efficiency means the sensor utilizes light signals more efficiently, enabling more effective light collection in low-light environments. It is particularly important for high-contrast shooting scenes, as it can simultaneously enhance detail in both dark and bright areas within a single image, significantly improving the sensor's dynamic range, restoring image details, and enhancing color saturation.

[0055] For existing image sensor pixel structures, limited by the gaps between on-chip microlenses 101 and the absorption and reflection of light by the materials in each part of the pixel structure itself, even with a back-illuminated (BSI) pixel structure with a shorter optical path, 5% to 21% of photons will still enter the pixel through the gaps between the on-chip microlenses 101. Some are absorbed by the metal mesh, while others enter the photodiodes of adjacent pixels after multiple reflections, forming optical crosstalk. Furthermore, when photons focused by the on-chip microlenses 101 pass through the interfaces between optical coatings and between the optical coatings and the semiconductor substrate 110, the abrupt change in refractive index causes reflected light, reducing the light signal entering the semiconductor substrate 110 and resulting in a decrease in quantum efficiency.

[0056] The embodiments described herein utilize a first structure 105-1 located between two adjacent color filter arrays 104 to isolate different colors and reduce crosstalk. When light leaks through the gap between the on-chip microlenses 101, the four sides of the second structure 105-2 provided by the present invention can collect the photons leaking through the gap between the on-chip microlenses 101 into the photodiode region 111, thereby reducing the reflectivity of photons entering the semiconductor substrate 110, increasing the total amount of effective light signals entering the semiconductor substrate 110, and improving the quantum efficiency of the image sensor.

[0057] Please refer to Figure 1 , Figure 1 This is a top view schematic diagram of a pixel structure for improving the quantum efficiency of an image sensor, provided as an embodiment of the present invention. Figure 1 As shown, the pixel structure includes:

[0058] A filter layer, which is formed by multiple color filter arrays 104.

[0059] In the embodiments described herein, the color filter array 104 is a standard RGGB Bayer array. The RGGB Bayer array (Bayer Pattern) is a common color filter array in digital image sensors. It captures color images by arranging red (R), green (G), blue (B) filters in a specific pattern above sensor pixels. It can be applied to smart devices such as digital cameras and mobile phone cameras. The color filter array 104 provided in this embodiment can also be referred to as a filter; multiple filters are arranged at equal intervals to form a filter layer for capturing color pixels.

[0060] Figure 2 This is a schematic diagram of the horizontal cross-section of an image sensor provided in an embodiment of the present invention. Figure 3 This is a structural schematic diagram of a diagonal cross-section of an image sensor provided in an embodiment of the present invention. The pixel structure layer includes a first structure 105-1 and a second structure 105-2. The bottom surfaces of the first structure 105-1 and the second structure 105-2 are flush. The highest point of the second structure 105-2 is higher than or flush with the highest point of the first structure 105-1. The first structure 105-1 is located between two adjacent color filter arrays 104. The length of the bottom surface of the second structure 105-2 is not less than the projected length of the gap. The second structure 105-2 is distributed at the gap positions of the four corners of the pixels of the color filter array 104. The gap is formed by adjacent on-chip microlenses 101 of the image sensor.

[0061] In the embodiments described herein, such as Figure 2 As shown, the first structure 105-1 is located between two adjacent color filter arrays 104, serving to isolate different colors and reduce crosstalk. Unlike traditional pixel structures that use tungsten as an anti-crosstalk material, this embodiment uses, but is not limited to, reflective aluminum. The first structure 105-1 extends into the lower passivation layer 106, collecting effective signals from pixel edges through surface reflection of the aluminum, while providing sufficient vertical extension space for the second structure 105-2. The bottom surface of the first structure 105-1 is connected to the bottom surface of the second structure 105-2. The height and width of the first structure 105-1 are determined based on the requirements and effectiveness of anti-crosstalk, and this embodiment does not impose any limitations on these dimensions.

[0062] like Figure 2As shown, the first structure 105-1 can be a sheet-like structure. Since it is located between two adjacent color filter arrays 104 and serves to isolate different colors and reduce crosstalk, its width should be as small as possible, and its height is related to the structure and height of the adjacent color filter arrays 104. The first structure 105-1 and the second structure 105-2 are connected to each other, dividing the multiple color filter arrays 104 into mutually independent array states.

[0063] like Figure 3 As shown, the second structure 105-2 is distributed at the gap positions of the four corners of the pixel. Its material is the same as that of the first structure 105-1, its lower surface is flush with the first structure 105-1, and its highest point is flush with or higher than the first structure 105-1. The four sides of a single second structure 105-2 are smooth planes, facing the center of the four surrounding pixels respectively. When light leaks through the gaps between the upper on-chip microlenses 101, the photons are reflected and collected into the photodiode region 111 by the four planes of the second structure 105-2. Preferably, the bottom surface of the second structure 105-2 coincides with the gap formed by the adjacent on-chip microlenses 101, so that the second structure 105-2 efficiently reflects the photons that are not collected by the on-chip microlenses 101 but enter through the gaps.

[0064] In some embodiments, the side of the second structure 105-2 faces the pixel center of the color filter array 104.

[0065] Specifically, in order to collect photons from the four pixels of the color filter array 104, the second structure 105-2 provided in this embodiment needs to have a three-dimensional structure with four sides. In this embodiment, the shape of the second structure 105-2 is a pyramid shape, with a square base. That is, the second structure 105-2 provided in this embodiment adopts a regular pyramid shape. This shape facilitates the alignment of the sides of the second structure 105-2 with the pixel center of the color filter array 104, making it easier to reflect the photons collected by the on-chip microlens 101 onto the photodiode disposed within the semiconductor substrate 110. It should be noted that in this embodiment, the color filter array 104 uses a standard RGGB Bayer array, with multiple filters arranged at equal intervals to form a filter layer for capturing color pixels. Therefore, the base of the second structure 105-2 is square. However, in other array arrangements, the multiple filters may not be arranged at equal intervals, and thus the base of the second structure 105-2 is not square.

[0066] In some embodiments, the angle and height formed by the side surface and the vertical direction of the second structure 105-2 satisfy the following relationship: [tan(∠2α) * Hpyr]<( * Pitch) / 2, where Pitch represents the size of a single pixel, α represents the angle formed by each side of the second structure 105-2 and the vertical direction, and Hpyr represents the height of the second structure 105-2.

[0067] In the embodiments described herein, due to the spatial constraints of the optical structure in the BSI pixel process, the pyramid-shaped second structure 105-2 is typically selected based on the maximum height allowed by space. The specific dimensions of the second structure 105-2 need to be designed with a compromise between the pixel structure and simulation results. Compared to traditional extinction materials, this invention uses a total internal reflection material to improve photon utilization efficiency. Simultaneously, a second structure 105-2 is used at the four corners of the pixel where crosstalk and QE loss are prone to occur, enhancing photon collection capabilities. Figure 1 As shown, a reflective plane is provided in the area not covered by the on-chip microlens 101, so that photons that leak from the gap between adjacent on-chip microlenses 101 reach the area of ​​the photodiode through reflection, forming an effective quantum efficiency.

[0068] Since the pixel arrangement can vary in size and spacing, the shape of the bottom surface of the second structure can also be adjusted according to the pixel arrangement.

[0069] Regarding the second structure 105-2 provided in the embodiments described herein, the second structure 105-2 is fabricated using an etch-back process. Since the photoresist is also etched during the material etching process, the morphology of the finished product is controlled by the difference in solubility between the photoresist and the etched material. The photoresist can be formed by diffraction through small holes in a mask, allowing the photoresist to be exposed to light of different intensities, creating regions with different solubilities. A more specific implementation method is as follows: for example, using... Figure 4 The photomask shown has aperture diameters ranging from 40 to 200 nm. When light passes through these apertures, it follows the Huygens-Fresnel principle, becoming a secondary light source at each aperture and propagating in the next instant. Adjacent secondary light sources superimpose during propagation, and the final light intensity illuminating the photoresist depends on the aperture diameter and distance between adjacent apertures. After exposure to different lighting conditions, the solubility of the photoresist in the etching solution gradually increases from the center to the edge. After etching back, a second structure 105-2 can be formed on the etched material. By selecting suitable materials to control the solubility difference between the photoresist and the etched material, the height of the formed second structure 105-2 can be controlled.

[0070] This invention also provides an image sensor, which is stacked from bottom to top. Therefore, the image sensor provided in this embodiment includes:

[0071] A semiconductor substrate 110, wherein a plurality of photodiode regions 111 are disposed thereon;

[0072] A dielectric layer 109 having a first refractive index is located on the semiconductor substrate 110;

[0073] A high-n-value anti-reflection layer 108 having a second refractive index is located on the dielectric layer 109;

[0074] A transition layer 107 having a third refractive index is located on the high n-value antireflective layer 108;

[0075] A passivation layer 106 having a fourth refractive index is located on the transition layer 107;

[0076] A pixel structure for improving the quantum efficiency of an image sensor, as described in the embodiments above, includes: a filter layer formed by a plurality of color filter arrays 104 at equal intervals; and a pixel structure layer including a first structure 105-1 and a second structure 105-2, wherein the bottom surfaces of the first structure 105-1 and the second structure 105-2 are flush, the highest point of the second structure 105-2 is higher than or flush with the highest point of the first structure 105-1, the first structure 105-1 is located between two adjacent color filter arrays 104, and the length of the bottom surface of the second structure 105-2 is not less than the projected length of the gap; wherein the gap is formed by adjacent on-chip microlenses 101 of the image sensor; and wherein the first structure 105-1 and the second structure 105-2 are at least partially embedded in the passivation layer 106.

[0077] Planarization layer 103, the planarization layer 103 being located on the filter layer; and

[0078] A microlens assembly, comprising an on-chip microlens 101 having a fifth refractive index and a lens antireflection layer 102 having a sixth refractive index, the microlens assembly being located on the planarization layer 103, and the lens antireflection layer 102 being located on the on-chip microlens 101.

[0079] For example, the on-chip microlens 101 has a fifth refractive index, and the lens anti-reflection layer 102 has a sixth refractive index. Typically, the microlens is made of a transparent material with the highest possible refractive index in order to achieve a light-gathering effect with a thinner thickness. The sixth refractive index of the lens anti-reflection layer 102 is preferably chosen to be the middle value between the fifth refractive index and the air refractive index. In this embodiment, the lens anti-reflection layer 102 can be silicon dioxide, and the thickness can be 100nm±10nm, which serves as the first anti-reflection layer.

[0080] The planarization layer 103, made of the same material as the on-chip microlens 101, is used to fill in the depressions generated during the fabrication of the filter.

[0081] The passivation layer 106 serves to isolate the working environment from humidity and prevent oxidation. At the same time, it can act as a second anti-reflection layer when it has a fourth refractive index. In this embodiment, the passivation layer 106 can be silicon nitride, silicon fluoride, aluminum nitride, titanium dioxide, aluminum oxide, or aluminum oxide compound, etc. By optimizing the thickness of the passivation layer 106, it can act as a second anti-reflection layer.

[0082] A high n-value antireflective layer 108 and a transition layer 107 are provided. The transition layer 107 has a third refractive index, and the high n-value antireflective layer 108 has a second refractive index. The transition layer 107 is located on one side of the passivation layer 106. In this embodiment, SiO2 material is preferably used. The high n-value antireflective layer 108 is located on one side of the semiconductor substrate 110. The fourth refractive index preferably has a real part size that is second only to the semiconductor substrate 110. In this embodiment, the high n-value antireflective layer 108 can be hafnium dioxide, tantalum pentoxide, titanium dioxide, aluminum arsenide, etc. By optimizing the thickness of the high n-value antireflective layer 108, it can play the role of a third antireflective layer.

[0083] The dielectric layer 109 has good surface insulation properties and needs to be transparent and have a first refractive index that is less than the second refractive index. In this embodiment, aluminum oxide is preferred.

[0084] Semiconductor substrate 110 includes a plurality of photodiode regions 111. As will be known to those skilled in the art, semiconductor substrate 110 may be silicon, silicon-germanium alloy, germanium, silicon carbide alloy, indium gallium arsenide alloy, any other alloy formed of group III-V compounds, combinations thereof, or bulk substrate thereof.

[0085] In the embodiments described herein, since light is reflected to varying degrees when passing through an interface composed of two media with different refractive indices, the greater the difference in the real parts of the refractive indices of the two media, the greater the reflected light will be. However, when a light wave passes through two reflective interfaces composed of three materials with different refractive indices, two different reflected lights will be generated and superimposed. By adjusting the thickness of the intermediate material, i.e., the antireflective layer, the reflected light generated by the two interfaces can be phase-shifted by 180 degrees. The phase-canceling reflected light energy will be superimposed on the incident light, resulting in less energy loss of the incident light.

[0086] Since the real part of the refractive index of air is 1.0 in the visible light range (400nm~700nm) and the real part of the refractive index of semiconductor substrate 110 is 4.6±0.9, about 30% of the light entering the semiconductor substrate 110 of the image sensor from the outside air will be reflected. Therefore, an anti-reflection structure is needed to weaken the reflected light and thus enhance the total amount of light entering the image sensor.

[0087] This embodiment employs a three-layer anti-reflection structure to improve optical transmittance. The three-layer anti-reflection structure includes a first anti-reflection structure composed of the lens anti-reflection layer 102 and the on-chip microlens 101; a second anti-reflection structure composed of the passivation layer 106 and the transition layer 107; and a third anti-reflection structure composed of the transition layer 107 and the high n-value anti-reflection layer 108. Compared with the prior art, the three-layer anti-reflection structure of the present invention, which uses high refractive index materials, can improve the optical transmittance of the image sensor by 5% to 10%, and further improve the quantum efficiency of the image sensor by increasing the incident light.

[0088] This invention also provides a method for manufacturing an image sensor, the method comprising:

[0089] A semiconductor substrate 110 is provided, wherein a plurality of photodiode regions 111 are disposed thereon; a dielectric layer 109 having a first refractive index is formed above the semiconductor substrate 110; a high n-value antireflective layer 108 having a second refractive index is formed above the dielectric layer 109; a transition layer 107 having a third refractive index is formed above the high n-value antireflective layer 108; a passivation layer 106 having a fourth refractive index is formed above the transition layer 107; and a pixel structure as described in the above embodiments for improving the quantum efficiency of an image sensor is formed above the passivation layer 106, wherein the pixel structure includes: a filter layer formed by a plurality of color filter arrays 104 at equal intervals; and a pixel structure layer including a first structure 105-1 and a second structure 105. -2, the bottom surfaces of the first structure 105-1 and the second structure 105-2 are flush, the highest point of the second structure 105-2 is higher than or flush with the highest point of the first structure 105-1, the first structure 105-1 is located between two adjacent color filter arrays 104, and the length of the bottom surface of the second structure 105-2 is not less than the projected length of the gap; wherein, the gap is formed by adjacent on-chip microlenses 101 of the image sensor; wherein, the first structure 105-1 and the second structure 105-2 are at least partially embedded in the passivation layer 106; a planarization layer 103 is formed above the filter layer; an on-chip microlens 101 with a fifth refractive index is formed above the planarization layer 103; and a lens anti-reflection layer 102 with a sixth refractive index is formed above the on-chip microlens 101.

[0090] Specifically, this invention proposes a three-layer anti-reflection structure including a lens anti-reflection layer 102, a passivation layer 106, and a high-n-value anti-reflection layer 108, wherein the thicknesses of the passivation layer 106, the high-n-value anti-reflection layer 108, and the intermediate transition layer 107 need to satisfy specific relationships. For example... Figure 5 As shown, in this embodiment, the high n-value antireflective layer 108 is made of tantalum pentoxide, and the real part of its refractive index is 2.1 when the incident light wavelength is 510 nm. The horizontal axis represents the thickness of the passivation layer 106, which is made of silicon nitride and has a thickness ranging from 10 nm to 170 nm; the vertical axis represents the transition layer 107, which is made of silicon dioxide and has a thickness ranging from 10 nm to 300 nm. Figure 5 In the middle, the higher the quantum efficiency, the darker the fill color, with a maximum of 78.8% and a minimum of 69.4%. To facilitate the illustration of the optimal thickness combination for quantum efficiency, the mesh outlines corresponding to conditions with quantum efficiency greater than 77.8% have been highlighted. (Comparison) Figure 5 According to the data, under the material combination of passivation layer 106, transition layer 107 and high n-value anti-reflection layer 108, the thickness of each layer made according to the method described in this invention can improve the quantum efficiency by a maximum of about 9.4%.

[0091] Generally, the real part of the second refractive index of the high-n-value antireflective layer 108 is 1.8 to 3.5, and the high-n-value antireflective layer 108 is a transparent material. The following describes the thickness combination relationship of the passivation layer 106, the transition layer 107, and the high-n-value antireflective layer 108 when the lens antireflective layer 102 is made of silicon dioxide with a thickness of 100 nm ± 15 nm, the passivation layer 106 is made of silicon nitride, and the transition layer 107 is made of silicon dioxide:

[0092] If the real part of the second refractive index of the high n-value antireflective layer 108 is within a first range, the high n-value antireflective layer 108 is formed according to a preset first thickness distribution function; wherein, the first thickness distribution function describes the distribution relationship between the thickness of the high n-value antireflective layer 108 and the real part of the second refractive index.

[0093] Specifically, based on the real part of the second refractive index described above, the first range provided in this embodiment is now defined as 1.8~3.5. When the real part of the second refractive index of the high n-value antireflective layer 108 is any value between 1.8 and 3.5, the thickness Th_ARC of the high n-value antireflective layer 108 and its real part N_ARC satisfy the relationship (2-1), that is, the first thickness distribution function, Th_ARC = 7.84 * N_ARC^2 – 65.64 * N_ARC + 161.19 (2-1). Based on the first thickness distribution function, as follows... Figure 6As shown, a graph is plotted showing the relationship between the real part value N_ARC and the thickness Th_ARC of the high n-value antireflection layer 108. The required range of the thickness Th_ARC of the high n-value antireflection layer 108 calculated based on Equation (2-1) is within ±10nm after satisfying Equation (2-1).

[0094] If the real part of the second refractive index is within the second range, and the thickness of the high n-value antireflective layer 108 conforms to the first thickness distribution function, a passivation layer 106 and a transition layer 107 are formed according to a preset second thickness distribution function; wherein, the second thickness distribution function describes the distribution relationship between the thickness of the passivation layer 106 and the thickness of the transition layer 107, and the second range is within the first range.

[0095] Specifically, when the real part N_ARC = 1.8~2.3, and under the premise of satisfying equation (2-1), the thickness x of the passivation layer 106 and the thickness y of the transition layer 107 satisfy equation (2-2), that is, the second thickness distribution function. Figure 7 To satisfy the first distribution relationship diagram of equation (2-2), the expression for the second thickness distribution function is as follows: y = -1.95E-08x5 + 7.32E-06x^4 - 8.55E-04x^3 + 3.27E-02x^2 - 5.05E-01x + 1.03E+02 (2-2). Similarly, the required range for the thickness x of the passivation layer 106 and the thickness y of the transition layer 107, calculated based on equation (2-2), is within ±10 nm after satisfying equation (2-2).

[0096] If the real part of the second refractive index is within the third range, and the thickness of the passivation layer 106 and the thickness of the transition layer 107 conform to the first thickness distribution function, the passivation layer 106 and the transition layer 107 are formed according to the preset third thickness distribution function; wherein, the third thickness distribution function describes the distribution relationship between the thickness of the passivation layer 106 and the thickness of the transition layer 107, and the third range is within the first range.

[0097] Specifically, when the real part N_ARC = 2.3~2.8, and under the premise of satisfying the relationship (2-1), the thickness x of the passivation layer 106 and the thickness y of the transition layer 107 satisfy the relationship (2-3), that is, the third thickness distribution function. Figure 8To satisfy the second distribution relationship diagram of equation (2-3), the expression for the third thickness distribution function is as follows: y = 65 * (N_ARC -2.45) * SIN((π / 95) * (x + 10)) + 132 (2-3). Similarly, the required range for the thickness x of the passivation layer 106 and the thickness y of the transition layer 107, calculated based on equation (2-3), is within ±10 nm after satisfying equation (2-3).

[0098] If the real part of the second refractive index is within the fourth range, and the thickness of the passivation layer 106 and the thickness of the transition layer 107 conform to the first thickness distribution function, the passivation layer 106 and the transition layer 107 are formed according to the preset fourth thickness distribution function; wherein, the fourth thickness distribution function describes the distribution relationship between the thickness of the passivation layer 106 and the thickness of the transition layer 107, and the fourth range is within the first range.

[0099] Specifically, when the real part N_ARC = 2.8~3.5, and under the premise of satisfying the relationship (2-1), the thickness x of the passivation layer 106 and the thickness y of the transition layer 107 satisfy the relationship (2-4), that is, the fourth thickness distribution function. Figure 9 To satisfy the third distribution relationship diagram of equation (2-4), the expression for the third thickness distribution function is as follows: y = -1.84E-09x^5 -1.27E-07x^4 + 1.69E-04x^3 - 1.78E-02x^2 + 2.21E-01x + 1.79E+02 (2-3). Similarly, based on equation (2-4), the required range for the thickness x of the passivation layer 106 and the thickness y of the transition layer 107 is within ±10nm after satisfying equation (2-4).

[0100] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pixel structure for boosting quantum efficiency of an image sensor, characterized by, The pixel structure comprises: a filter layer formed by a plurality of color filter arrays; and The pixel structure layer comprises a first structure and a second structure, the bottom surfaces of the first structure and the second structure are flush, the highest point of the second structure is higher than or flush with the highest point of the first structure, the first structure is located between two adjacent color filter arrays, the length of the bottom surface of the second structure is not less than the projection length of the gap, and the second structure is distributed at the gap position of the four corners of the color filter array pixel; wherein the gap is formed by adjacent on-chip microlenses of an image sensor; wherein the included angle formed by the side surface of the second structure and the vertical direction and the height satisfy the following relationship: [tan(∠2α)*Hpyr]<( Pitch) / 2, wherein Pitch represents the size of a single pixel, α represents the included angle formed by each side surface of the second structure and the vertical direction, and Hpyr represents the height of the second structure.

2. The pixel structure for improving quantum efficiency of an image sensor according to claim 1, wherein a side surface of the second structure faces a pixel center of the color filter array.

3. An image sensor, characterized by, The pixel structure comprises: a semiconductor substrate disposed with a plurality of photodiode regions; a dielectric layer having a first refractive index, the dielectric layer being located on the semiconductor substrate; a high-n-value anti-reflection layer having a second refractive index, the high-n-value anti-reflection layer being located on the dielectric layer; a transition layer having a third refractive index, the transition layer being located on the high-n-value anti-reflection layer; a passivation layer having a fourth refractive index, the passivation layer being located on the transition layer; The pixel structure for improving quantum efficiency of an image sensor according to any one of claims 1 to 2, wherein the pixel structure comprises: a filter layer formed by a plurality of color filter arrays; and a pixel structure layer comprising a first structure and a second structure, a bottom surface of the first structure and the second structure is flush, a highest point of the second structure is higher than or flush with a highest point of the first structure, the first structure is located between two adjacent color filter arrays, a length of the bottom surface of the second structure is not less than a projection length of a gap, the second structure is distributed at a gap position of four corners of a pixel of the color filter array; wherein the gap is formed by adjacent on-chip microlenses of the image sensor; wherein the first structure and the second structure are at least partially embedded in the passivation layer; a planar layer located on the filter layer; and a microlens group comprising an on-chip microlens having a fifth refractive index and a lens anti-reflection layer having a sixth refractive index, the microlens group being located on the planar layer, the lens anti-reflection layer being located on the on-chip microlens.

4. An image sensor as claimed in claim 3, characterized in that The first refractive index of the dielectric layer is less than the second refractive index of the high-n-value anti-reflection layer.

5. A method for fabricating an image sensor, characterized by, The method comprises: providing a semiconductor substrate disposed with a plurality of photodiode regions; forming a dielectric layer having a first refractive index above the semiconductor substrate; forming a high-n-value anti-reflection layer having a second refractive index above the dielectric layer; forming a transition layer having a third refractive index above the high-n-value anti-reflection layer; forming a passivation layer having a fourth refractive index above the transition layer; Forming a pixel structure for improving quantum efficiency of an image sensor on the passivation layer, the pixel structure comprising: a filter layer formed by a plurality of color filter arrays; and a pixel structure layer comprising a first structure and a second structure, the first structure and the second structure having a flush bottom surface, the second structure having a highest point higher than or flush with a highest point of the first structure, the first structure being located between two adjacent color filter arrays, the second structure having a bottom surface with a length not less than a projected length of a gap, the second structure being distributed at the gap positions of four corners of the color filter array pixels; wherein the gap is formed by adjacent on-chip microlenses of the image sensor; wherein the first structure and the second structure are at least partially embedded in the passivation layer. Forming a planarization layer on the filter layer; Forming an on-chip microlens having a fifth refractive index on the planarization layer; and Forming a lens anti-reflection layer having a sixth refractive index on the on-chip microlens.

6. A method for fabricating an image sensor according to claim 5, wherein, If the real part of the second refractive index of the high-n anti-reflection layer is within a first range, forming the high-n anti-reflection layer according to a preset first thickness distribution function; wherein the first thickness distribution function describes a distribution relationship between the thickness of the high-n anti-reflection layer and the real part of the second refractive index.

7. A method for fabricating an image sensor according to claim 6, wherein, If the real part of the second refractive index is within a second range and the thickness of the high-n anti-reflection layer conforms to the first thickness distribution function, forming the passivation layer and the transition layer according to a preset second thickness distribution function; wherein the second thickness distribution function describes a distribution relationship between the thickness of the passivation layer and the thickness of the transition layer, and the second range is within the first range.

8. The method for fabricating an image sensor according to claim 6, wherein If the real part of the second refractive index is within a third range and the thickness of the passivation layer and the thickness of the transition layer conform to the first thickness distribution function, forming the passivation layer and the transition layer according to a preset third thickness distribution function; wherein the third thickness distribution function describes a distribution relationship between the thickness of the passivation layer and the thickness of the transition layer, and the third range is within the first range.

9. The method for fabricating an image sensor according to claim 6, wherein, If the real part of the second refractive index is within a fourth range and the thickness of the passivation layer and the thickness of the transition layer conform to the first thickness distribution function, forming the passivation layer and the transition layer according to a preset fourth thickness distribution function; wherein the fourth thickness distribution function describes a distribution relationship between the thickness of the passivation layer and the thickness of the transition layer, and the fourth range is within the first range.

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