An image sensor and method of fabrication
By introducing isolation cavities and anti-reflection layers into the image sensor, the signal crosstalk problem was solved, the optical performance and signal-to-noise ratio of the image sensor were improved, and the image quality was enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- WUHAN CHUXING TECH CO LTD
- Filing Date
- 2024-12-25
- Publication Date
- 2026-06-26
AI Technical Summary
In existing image sensors, signal crosstalk issues lead to a decline in optical performance, especially light leakage and signal interference between the filter and lens layers, which affect image quality.
An isolation cavity is introduced into the image sensor, including a first sub-isolation cavity and a second sub-isolation cavity located between the filter and the lens unit. Air is used to isolate adjacent structures to reduce light escape and signal crosstalk, and a partial cavity opening is closed by an anti-reflective layer to improve optical performance.
It effectively reduces light leakage between lens units and signal crosstalk between filters, improves the optical performance and signal-to-noise ratio of the image sensor, and enhances image quality in low-light environments.
Smart Images
Figure CN122294609A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, and in particular to an image sensor and its fabrication method. Background Technology
[0002] Currently, the core structure of an image sensor is a photoelectric conversion unit, and the core component of this unit is a photodiode. Typically, the photoelectric conversion unit of an image sensor includes multiple photodiodes arranged in an array. The photodiodes convert the collected photons into electrons, and then, through other auxiliary circuit structures, convert these electrons into electrical signals for output.
[0003] In existing technologies, image sensors include a substrate, a lens layer, and filters. The filters are arranged in an array, with a lens covering the top of the filters. Incident light passes through the lens layer and converges onto the filters. Different color filters have different transmittance for various colors of light, thus achieving the conversion and output of different color light signals. Light passing through the lens layer and filters may escape and cause crosstalk in adjacent lens remnants, thereby affecting the optical performance of the image sensor. Summary of the Invention
[0004] The embodiments of this application provide an image sensor and its fabrication method. The image sensor improves optical performance by adding an isolation cavity to solve the problem of signal crosstalk.
[0005] The embodiments of this application adopt the following technical solutions:
[0006] In a first aspect, some embodiments of this application provide an image sensor, which includes: a substrate, a filter layer, and a lens layer; the substrate includes a light-receiving surface and a backlight surface facing each other; the filter layer is located on one side of the light-receiving surface of the substrate, and the filter layer includes a variety of filters arranged in an array at intervals; the lens layer is located on the side of the filter layer away from the substrate, and the lens layer includes a variety of lens units arranged in an array at intervals, with each filter corresponding to a lens unit; wherein, the corresponding filters and lens units form a filter lens group, and an isolation cavity is formed between each two adjacent filter lens groups.
[0007] Based on the above solution, this application provides an image sensor that can solve the signal crosstalk problem by adding an isolation cavity. The isolation cavity first separates adjacent lens units with air, reducing light escape and minimizing mutual interference between lens units. Simultaneously, the isolation cavity also separates adjacent filters with air, reducing signal crosstalk between filters. Incident light passes through the filters to reach the corresponding photosensitive device without affecting adjacent filters, thereby improving the optical performance of the image sensor.
[0008] As one possible implementation, the isolation cavity includes a first sub-isolation cavity and a second sub-isolation cavity; the first sub-isolation cavity is located between two adjacent filters, and the second sub-isolation cavity is located between two adjacent lens units.
[0009] As one possible implementation, the image sensor further includes: an anti-reflective layer located on the side of the lens layer away from the substrate; and at least partially isolating the cavity having a first opening on the side away from the substrate, wherein the anti-reflective layer closes at least partially the first opening.
[0010] As one possible implementation, the anti-reflective layer is also attached to the inner wall of the isolation cavity.
[0011] As one possible implementation, the anti-reflective layer fills part of the bottom space of the isolation cavity.
[0012] As one possible implementation, the image sensor also includes: multiple isolation walls and multiple photosensitive devices disposed inside the substrate; each isolation wall corresponds to an isolation cavity position and extends to the light-receiving surface of the substrate; the multiple photosensitive devices are located on the side of the multiple isolation walls away from the multiple filters, and each photosensitive device corresponds to a filter position.
[0013] Secondly, some embodiments of this application provide a method for fabricating an image sensor, comprising: providing a substrate, the substrate including a light-receiving surface and a backlight surface opposite to each other; forming a filter layer on one side of the light-receiving surface of the substrate, the filter layer including a plurality of filters arranged in an array at intervals; forming a lens layer on the side of the filter layer away from the substrate, the lens layer including a plurality of lens units arranged in an array at intervals, each filter correspondingly covering a corresponding lens unit; wherein, the corresponding filters and lens units constitute a filter lens group, and an isolation cavity is formed between each two adjacent filter lens groups.
[0014] The beneficial effects of the second aspect can be referred to the beneficial effects of the first aspect, and will not be repeated here.
[0015] As one possible implementation, forming the isolation cavity further includes: before forming the filter layer on the light-receiving side of the substrate, forming a photoresist layer on the light-receiving side of the substrate, and patterning the photoresist layer to form a grid-like photoresist layer; multiple filters are located one-to-one within the grid of the grid-like photoresist layer.
[0016] An initial lens layer is formed on the side of the filter layer away from the substrate. The initial lens layer is patterned to form a lens layer, and at least part of the mesh-like photoresist layer between two adjacent lens units in the lens layer is exposed. The mesh-like photoresist layer is removed to form an isolation cavity.
[0017] As one possible implementation, the fabrication method further includes: after forming the isolation cavity, forming an anti-reflection layer on the side of the lens layer away from the substrate; at least a portion of the isolation cavity has a first opening on the side away from the substrate, and the anti-reflection layer closes at least a portion of the first opening. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in some embodiments of this application will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual flow of the method, the actual timing of the signals, etc. involved in the embodiments of this application.
[0019] Figure 1 This is a schematic diagram of an existing image sensor;
[0020] Figure 2 A schematic diagram of an image sensor provided for some embodiments of this application;
[0021] Figure 3 A schematic diagram of another image sensor provided for some embodiments of this application;
[0022] Figure 4 A schematic diagram of yet another image sensor provided for some embodiments of this application;
[0023] Figure 5 A top view of an image sensor provided for some embodiments of this application;
[0024] Figure 6 A schematic diagram of an anti-reflective layer provided for some embodiments of this application;
[0025] Figure 7 A schematic diagram of another anti-reflective layer provided for some embodiments of this application;
[0026] Figure 8 A schematic diagram of yet another anti-reflective layer provided for some embodiments of this application;
[0027] Figure 9 A schematic diagram of yet another anti-reflective layer provided for some embodiments of this application;
[0028] Figure 10 A flowchart of image sensor fabrication is provided for some embodiments of this application;
[0029] Figure 11 A flowchart of another image sensor fabrication process provided for some embodiments of this application;
[0030] Figure 12 A flowchart illustrating the fabrication of yet another image sensor, provided for some embodiments of this application;
[0031] Figure 13 A flowchart illustrating another image sensor fabrication method provided for some embodiments of this application.
[0032] Among them, 1 is the substrate; 101 is the light-receiving surface; 102 is the backlight surface; 2 is the filter layer; 21 is the filter; 3 is the lens layer; 31 is the lens unit; 32 is the edge portion; 4 is the filter lens group; 5 is the anti-reflection layer; 6 is the isolation wall; 7 is the photosensitive device; N1 is the isolation cavity; N11 is the first sub-isolation cavity; N12 is the second sub-isolation cavity; and 100 is the image sensor. Detailed Implementation
[0033] The technical solutions in some embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application are within the scope of protection of this application.
[0034] In the description of this application, it should be understood that, unless the context requires otherwise, the term "comprising" is interpreted as open-ended and encompassing, meaning "including, but not limited to," throughout the specification and claims. In the description, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "exemplarily," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this application. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.
[0035] Hereinafter, the terms "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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more.
[0036] The use of “applies to” or “configured to” in this article implies an open and inclusive language that does not preclude applicability to or configuration to devices that perform additional tasks or steps.
[0037] Currently, the core structure of an image sensor is a photoelectric conversion unit, and the core component of this unit is a photodiode. Typically, the photoelectric conversion unit of an image sensor includes multiple photodiodes arranged in an array. The photodiodes convert the collected photons into electrons, and then, through other auxiliary circuit structures, convert these electrons into electrical signals for output.
[0038] In existing technologies, image sensors include a substrate, a lens layer, and filters. The filters are arranged in an array, with the lens layer covering the top of the filters. Incident light passes through the lens layer and converges onto the filters. Different color filters have different transmittance for different colors of light, thus achieving the conversion and output of different color light signals. Light passing through the lens layer and filters can escape and cause crosstalk in adjacent lenses, thereby affecting the optical performance of the image sensor.
[0039] For example, refer to Figure 1 The image sensor also includes an anti-reflective coating (ARC), which covers the lens layer. Incident light, under the influence of the anti-reflective coating, passes through the lens layer and converges onto the filter. Different color filters have different transmittance for various colors of light, thus achieving the conversion and output of different color light signals. Light passing through the lens layer and filters can escape and cause crosstalk in adjacent lenses, thereby affecting the optical performance of the image sensor.
[0040] To solve the problem of signal crosstalk Figure 1 A light-blocking structure is placed between the filters to block light. Firstly, this light-blocking structure is placed between the filters, which reduces signal crosstalk between the filters, but light can still escape between the lenses.
[0041] Meanwhile, the light-blocking structure is made of backside metal grid (BMG) material, which is not a suitable low-refractive-index material. Therefore, the light entering the filter will still cause crosstalk between the filters, which will still affect the optical performance of the image sensor.
[0042] It should be noted that an anti-reflective layer (ARC) is a special coating applied to photolithography layers. ARC is designed to reduce reflections on the surface of optical devices, increase transmittance, and enhance optical performance. In image sensors, ARC can reduce light loss and interference caused by light reflection, thereby improving image quality and signal-to-noise ratio. This is achieved by forming a thin-film coating with a refractive index and impedance that matches the surrounding medium, minimizing the reflection coefficient when incident light is transmitted at the interface between the medium and the thin film.
[0043] The primary function of a filter is to adjust the spectral response of each pixel in an image sensor. By using filters of different colors, the image sensor can sense and separate different colors of light and convert them into digital signals. In this way, the image sensor can capture color images.
[0044] Crosstalk refers to signal interference between pixels. Specifically, crosstalk occurs when the photosensitive areas of each color channel overlap due to factors such as different modules and manufacturing processes. This causes a pixel's signal to be affected not only by the light signal received by its own photosensitive element but also by the light signals received by the photosensitive elements of adjacent pixels. Ideally, each RGB pixel passing through a color filter would only sense light of its corresponding color. However, in practical applications, due to the crosstalk effect, a pixel cannot be completely excited by the light from one color channel and will be interfered with by the light signals from adjacent pixels. This interference can lead to a decrease in image quality, such as the generation of false colors and a reduced signal-to-noise ratio.
[0045] In view of this, some embodiments of this application provide an image sensor 100, such as Figure 2 As shown, the image sensor 100 includes: a substrate 1, a filter layer 2, and a lens layer 3.
[0046] The substrate 1 includes a light-receiving surface 101 and a backlight surface 102 facing each other; the filter layer 2 is located on one side of the light-receiving surface 101 of the substrate 1, and the filter layer 2 includes a variety of filters 21, which are arranged in an array at intervals.
[0047] The lens layer 3 is located on the side of the filter layer 2 away from the substrate 1. The lens layer 3 includes multiple lens units 31, which are arranged in an array at intervals. Each lens unit 31 covers a filter 21.
[0048] Among them, the corresponding filter 21 and lens unit 31 are filter lens groups 4, and an isolation cavity N1 is formed between each two adjacent filter lens groups 4.
[0049] In other words, an isolation cavity N1 is formed between the two filters 21 and between the two lens units 31. This reduces signal crosstalk between the filters 21 and prevents light from escaping between the lens units 31.
[0050] The isolation cavity N1 is essentially air isolation. Under standard conditions (i.e., specific temperature, pressure, and air composition), the refractive index of air for visible light is approximately 1.00029. This value is very close to 1, indicating that air's refractive effect on light is relatively weak.
[0051] Because air has a low refractive index, incident light is less likely to travel from one lens unit 31 to another, which reduces light escape. At the same time, crosstalk between filters 21 is less likely to occur.
[0052] In some embodiments, the lens layer 3 is made of resin.
[0053] In some embodiments, the filter 21 includes three colors: red, green, and blue. When four adjacent filters 21 are arranged in a 2×2 configuration, two green filters 21 are diagonally positioned, and one red filter 21 and one blue filter 21 are diagonally positioned.
[0054] Based on the above solution, this application provides an image sensor 100, which can solve the signal crosstalk problem by adding an isolation cavity N1. The isolation cavity N1 first separates adjacent lens units 31 with air, which can reduce light escape and reduce the mutual influence between lens units 31; at the same time, the isolation cavity N1 also separates adjacent filters 21 with air, which can reduce signal crosstalk between filters 21. The incident light will pass through the filter 21 and enter the corresponding photosensitive device without affecting the adjacent filter 21, thereby improving the optical performance of the image sensor 100.
[0055] like Figure 3 As shown, the isolation cavity N1 includes a first sub-isolation cavity N11 and a second sub-isolation cavity N12.
[0056] The first sub-isolation cavity N11 is located between two adjacent filters 21, and the second sub-isolation cavity N12 is located between two adjacent lens units 31.
[0057] In some embodiments, the size of the first sub-isolation cavity N11 in the first direction is equal to the size of the second sub-isolation cavity N12 in the first direction, where the first direction is the arrangement direction of two adjacent filters 21.
[0058] The first sub-isolation cavity N11 and the second sub-isolation cavity N12 are connected. The first sub-isolation cavity N11 is mainly located between two adjacent filters 21 and is used to reduce signal crosstalk between filters 21. When incident light enters the filter 21, it will be refracted. However, the refractive effect of the first sub-isolation cavity N11 is relatively weak. At least most of the incident light will pass through the corresponding filter 21 and be separated into the three basic colors of red, green, and blue, so that the photosensitive device can sense and convert it into the corresponding electrical signal. Since most of the incident light is separated by the filter 21, the final electrical signal is closer to the true value.
[0059] The second sub-isolation cavity N12 is mainly located between two adjacent lens units 31 and is used to reduce light escape. The incident light is first focused by the lens unit 31 and then incident on the filter 21. The lens unit 31 is used to collect and focus the incident light. When the incident light enters the lens unit 31, it will be refracted and escaped, which may cause the escaped photons to enter the adjacent lens unit 31. However, the refractive effect of the second sub-isolation cavity N12 is relatively weak, and the escaped photons cannot be transmitted to the adjacent lens unit 31 through the second sub-isolation cavity N12. Thus, all photons can be focused onto the corresponding filter 21.
[0060] In some embodiments, the first sub-isolation cavity N11 and the second sub-isolation cavity N12 described above are both located between the filter lens group 4. Generally, the lens unit 31 in the filter lens group 4 is a convex lens, and the convex lens is a plano-convex lens, that is, one side is convex and the other side is flat.
[0061] Reference Figure 4 Among them, the isolation cavity N1 is grid-shaped. The grid-shaped structure can usually provide stronger structural support because it has connection and support points in multiple directions. This design can increase the overall stability and durability.
[0062] like Figure 5 As shown, the image sensor 100 further includes: an anti-reflection layer 5 located on the side of the lens layer 3 away from the substrate 1; at least a portion of the isolation cavity N1 has an opening on the side away from the substrate 1, and the anti-reflection layer 5 closes the opening of the isolation cavity N1 on the side away from the substrate 1.
[0063] At least partially refers to a portion of the isolation cavity N1 having an opening (see reference). Figure 7 Another part is not open, and is made by connecting with other isolation cavities N1 (see reference). Figure 6 ).
[0064] Figure 6 The isolation cavity N1 in the middle has no opening. Figure 7 The isolation cavity N1 has an opening. Furthermore, the opening of the isolation cavity N1 varies in size.
[0065] The fact that the isolation cavity N1 has no opening means that the part of the lens did not penetrate the photoresist during the etching process, which is a process issue. However, at least part of the isolation cavity N1 has an opening, so it will not affect subsequent fabrication.
[0066] The main function of the anti-reflective layer 5 is to reduce light reflection. By reducing reflection, the anti-reflective layer 5 allows more light to pass through the lens unit 31 and enter the image sensor 100. This increases light utilization, enabling the image sensor 100 to capture more light information.
[0067] For example, in low-light environments, more light can enter the image sensor 100, and more light information means a higher signal-to-noise ratio and better image quality.
[0068] Meanwhile, the anti-reflective layer 5 not only reduces reflection, but also acts as a protective film to seal the opening of the isolation cavity N1. This helps prevent dust, moisture and other contaminants from entering the isolation cavity, thereby protecting the internal structure and performance of the image sensor 100 without affecting the function of the isolation cavity N1.
[0069] In some embodiments, refer to Figure 8 The anti-reflective layer 5 is also attached to the top inner wall X1, bottom inner wall X2 and side inner wall X3 of the isolation cavity N1.
[0070] In some embodiments, refer to Figure 9 The anti-reflective layer 5 fills part of the space in the isolation cavity N1. In other words, part of the anti-reflective layer 5 occupies a portion of the isolation cavity N1.
[0071] In summary, in the image sensor 100, incident light enters the image sensor 100 through the lens layer 3 and reaches the photosensitive element through a series of optical paths. The anti-reflection layer 5 not only reduces reflection and scattering but also optimizes the optical path, enabling light to reach the photosensitive element more efficiently.
[0072] In some embodiments, refer to Figure 10 The image sensor 100 also includes a plurality of isolation walls 6 and a plurality of photosensitive elements 7, which are disposed inside the substrate 1. Each isolation wall 6 corresponds to an isolation cavity N1 and extends to the light-receiving surface 101 of the substrate 1.
[0073] Multiple photosensitive devices 7 are located on the side of multiple isolation walls 6 away from multiple filters 21, and each photosensitive device 7 corresponds to one filter 21. That is, there is one photosensitive device 7 below each filter 21.
[0074] The isolation barrier 6 effectively isolates adjacent photosensitive devices 7, preventing interference between their optical or electrical signals. This helps ensure that each photosensitive device 7 can accurately receive and convert the corresponding optical signal, thereby improving the overall clarity and accuracy of the image.
[0075] Meanwhile, the isolation wall 6 not only serves as an isolation element but also acts as a supporting structure within the substrate 1, enhancing the mechanical stability of the entire image sensor 100. This helps prevent structural deformation or damage caused by external forces during manufacturing, transportation, or use.
[0076] In some embodiments, the photosensitive device 7 is a photodiode.
[0077] Secondly, some embodiments of this application provide a method for manufacturing an image sensor 100, comprising:
[0078] S1, Provide substrate 1.
[0079] The substrate 1 includes a light-receiving surface 101 and a backlighting surface 102.
[0080] Reference Figure 10 First, prepare a substrate 1 without a mesh structure. This substrate 1 can be a silicon wafer, a glass sheet, or other substrate 1 material used for semiconductor or micro / nano manufacturing.
[0081] S2. A filter layer 2 is formed on one side of the light-receiving surface 101 of the substrate 1.
[0082] The filter layer 2 includes a variety of filters 21, which are arranged in an array and spaced apart.
[0083] Reference Figure 10 A photoresist capable of both positive and negative development and resistant to high temperatures is coated onto this substrate 1. This photoresist has special chemical properties, enabling it to exhibit both positive and negative development characteristics during exposure and development, and it can withstand high-temperature processing.
[0084] S3. A lens layer 3 is formed on the side of the filter layer 2 away from the substrate 1.
[0085] The lens layer 3 includes multiple lens units 31, which are arrayed and spaced apart. Each filter 21 is covered by a corresponding lens unit 31. The corresponding filter 21 and lens unit 31 form a filter lens group 4, and an isolation cavity N1 is formed between each two adjacent filter lens groups 4.
[0086] S2. Before forming the filter layer 2 on one side of the light-receiving surface 101 of the substrate 1, the method further includes:
[0087] S02. A photoresist layer is formed on one side of the light-receiving surface 101 of the substrate 1, and the photoresist layer is patterned to form a mesh-like photoresist layer.
[0088] Reference Figure 10 A mask pattern is formed on a substrate 1 coated with photoresist using methods such as photolithography or electron beam etching. This mask pattern determines the shape and position of the final mesh-like photoresist. A light source is then used to expose the portion of the photoresist not covered by the mask pattern.
[0089] During exposure, the chemical properties of the photoresist change, causing the exposed and unexposed areas to exhibit different solubilities in the subsequent development process. An aqueous solvent is used for positive development of the exposed photoresist. During positive development, the exposed photoresist is dissolved and removed by the solvent, while the unexposed areas remain. Because photoresist has the characteristic of positive and negative development, this step results in the formation of a pattern identical to the mask pattern.
[0090] In some embodiments, the photoresist described above has high temperature resistance, so the mesh-like photoresist can remain stable in subsequent high-temperature processing steps and will not deform or fail due to temperature rise.
[0091] The above-described process can be used to manufacture various microstructures, especially mesh-like structures requiring precise control of shape and position. By adjusting the mask pattern and exposure conditions, mesh-like photoresists with different sizes, shapes, and spacings can be produced to meet diverse manufacturing needs.
[0092] S2. A filter layer 2 is formed on one side of the light-receiving surface 101 of the substrate 1, including:
[0093] S21. A filter layer 2 is formed on one side of the light-receiving surface 101 of the substrate 1. The filter layer 2 includes a plurality of filters 21, which are located one-to-one within the grid of the mesh-like photoresist layer.
[0094] For example, refer to Figure 11 First, a green filter layer is formed on one side of the light-receiving surface 101 of the substrate 1. Then, the green filter layer that needs to be retained is exposed and processed, while the unwanted green filter layer is developed and removed, thus forming the desired filter layer. Figure 11 The pattern in S201 forms the first filter (green filter) 211.
[0095] Then, a red filter layer is formed on top of the green filter layer. The desired red filter layer is then exposed to the light, while the unwanted red filter layer is developed and removed. Figure 11 The pattern in S202 forms the second filter (red filter) 212.
[0096] Finally, a blue filter layer is formed on top of the red filter layer. The desired blue filter layer is then exposed to the light, while the unwanted blue filter layer is developed and removed. Figure 11 The pattern in S203 forms the third filter (blue filter) 213.
[0097] In S201, S202, and S203, the patterns are top views of the image sensor 100, and the corresponding cross-sectional view is on the right.
[0098] like Figure 12 As shown, the preparation method also includes:
[0099] S3. A lens layer 3 is formed on the side of the filter layer 2 away from the substrate 1, including:
[0100] S31. An initial lens layer is formed on the side of the filter layer 2 away from the substrate 1. The initial lens layer is patterned to form a lens layer 3, and at least part of the mesh-like photoresist layer between two adjacent lens units 31 in the lens layer 3 is exposed. The mesh-like photoresist layer is removed to form an isolation cavity N1.
[0101] A lens material is coated onto the aforementioned filter layer 2. After coating, a softening process is performed. The purpose of this step is to soften and allow the lens material to flow at high temperatures, thereby forming a smooth and regular lens surface. This thermal reflow process is crucial for ensuring the optical performance and consistency of the lens.
[0102] After the softening process, the lens is etched. The purpose of this step is to form a lens unit 31 with specific optical properties by precisely controlling the depth and shape of the etching. The etching process can adjust parameters such as the focal length and curvature of the lens unit 31, thereby optimizing the performance of the image sensor 100.
[0103] During the lens etching process, the etching depth and range need to be precisely controlled to ensure that the mesh-like photoresist is exposed in the gaps between the lens units 31. The etching process stops once the predetermined depth is reached and the mesh-like photoresist is successfully exposed.
[0104] It should be noted that the lens material consists of two types. The top layer of lens material is softened to form a template, while the bottom layer of lens material has already been solidified. Then, the template is used as a standard for etching to ultimately form the shape of the template, which is the flat lens.
[0105] Reference Figure 13 The preparation method also includes:
[0106] S4. After removing the mesh-like photoresist layer to form the isolation cavity N1, an anti-reflection layer 5 is formed on the side of the lens layer 3 away from the substrate 1.
[0107] An anti-reflective layer 5 is formed on the lens layer 3 by a deposition process. The anti-reflective layer 5 is an oxide with excellent insulation and chemical stability, which seals the opening of the isolation cavity N1.
[0108] Before forming the anti-reflection layer 5, a special organic solvent is selected to remove the mesh-like photoresist. After the mesh-like photoresist is removed, air enters, thereby forming an isolation cavity N1.
[0109] In summary, a closed cavity structure with an optimal low refractive index is ultimately formed between the filter lens groups 4, which can reduce signal crosstalk between the filter lens groups 4. The incident light will pass through the filter and enter the corresponding photosensitive device without affecting the adjacent filter, thereby improving the optical performance of the image sensor.
[0110] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. An image sensor, characterized in that, The image sensor includes: A substrate, the substrate comprising an opposing light-receiving surface and a backlighting surface; A filter layer is located on one side of the light-receiving surface of the substrate. The filter layer includes a variety of filters arranged in an array at intervals. A lens layer is located on the side of the filter layer away from the substrate. The lens layer includes multiple lens units, which are arranged in an array at intervals. Each filter is covered by a corresponding lens unit. Among them, the corresponding filter and lens unit is a filter lens group, and an isolation cavity is formed between each two adjacent filter lens groups.
2. The image sensor according to claim 1, characterized in that, The isolation cavity includes a first sub-isolation cavity and a second sub-isolation cavity; The first sub-isolation cavity is located between two adjacent filters, and the second sub-isolation cavity is located between two adjacent lens units.
3. The image sensor according to claim 1 or 2, characterized in that, The image sensor further includes an anti-reflective layer located on the side of the lens layer away from the substrate; At least a portion of the isolation cavity has a first opening on a side away from the substrate, and the anti-reflective layer closes the at least a portion of the first opening.
4. The image sensor according to claim 3, characterized in that, The anti-reflective layer is attached only to the top of the isolation cavity.
5. The image sensor according to claim 3, characterized in that, The anti-reflective layer is also attached to the inner wall of the isolation cavity.
6. The image sensor according to claim 5, characterized in that, The anti-reflective layer fills part of the bottom space of the isolation cavity.
7. The image sensor according to claim 1, characterized in that, The image sensor further includes: multiple isolation walls and multiple photosensitive devices, wherein the multiple isolation walls and multiple photosensitive devices are disposed inside the substrate; Each of the isolation walls corresponds to one of the isolation cavities, and the isolation walls extend to the light-receiving surface of the substrate; The plurality of photosensitive devices are located on the side of the plurality of isolation walls away from the plurality of filters, and each photosensitive device corresponds to one of the filter positions.
8. A method for fabricating an image sensor, characterized in that, include: A substrate is provided, the substrate comprising an opposing light-receiving surface and a backlighting surface; A filter layer is formed on one side of the light-receiving surface of the substrate. The filter layer includes a variety of filters, which are arranged in an array at intervals. A lens layer is formed on the side of the filter layer away from the substrate. The lens layer includes a plurality of lens units, which are arranged in an array at intervals. Each filter is covered with a corresponding lens unit. Among them, the corresponding filter and lens unit is a filter lens group, and an isolation cavity is formed between each two adjacent filter lens groups.
9. The preparation method according to claim 8, characterized in that, The method for forming the isolation cavity further includes: Before forming a filter layer on the light-receiving side of the substrate, a photoresist layer is formed on the light-receiving side of the substrate, and the photoresist layer is patterned to form a mesh-like photoresist layer. The various filters are located one-to-one within the grid of the mesh-like photoresist layer; An initial lens layer is formed on the side of the filter layer away from the substrate. The initial lens layer is patterned to form the lens layer, and at least a portion of the mesh-like photoresist layer between two adjacent lens units is exposed in the lens layer. The mesh-like photoresist layer is removed to form the isolation cavity.
10. The preparation method according to claim 9, characterized in that, The preparation method further includes: After the isolation cavity is formed, an anti-reflective layer is formed on the side of the lens layer away from the substrate; at least a portion of the isolation cavity has a first opening on the side away from the substrate, and the anti-reflective layer closes the at least a portion of the first opening.