Image sensor and manufacturing method therefor, camera module, and electronic device

Abstract

Embodiments of the present application relate to the technical field of imaging. Disclosed are an image sensor and a manufacturing method therefor, a camera module, and an electronic device. The manufacturing method comprises: using a silicon-containing gas and an oxygen-containing gas to form an isolation dielectric layer on a filter array layer within a preset temperature range and a preset pressure range and at a first preset radio frequency power; using the silicon-containing gas and a nitrogen-containing gas to form a dielectric thin film on the isolation dielectric layer within the preset temperature range and the preset pressure range and at a second preset radio frequency power, wherein the dielectric thin film has a refractive index greater than or equal to 1.8; and etching the dielectric thin film to form a metasurface array layer, wherein the metasurface array layer is configured to disperse incident light and transmit dispersed light to the filter array layer. The silicon-containing gas comprises an inert gas, and the maximum value of the preset temperature range is less than 230°C. The manufacturing method can improve the light utilization rate, enables deposition of a dielectric thin film while protecting the filter array layer, and mitigates trace metal contamination.

Description

Image sensors and their fabrication methods, camera modules, electronic devices

[0001] This application claims priority to Chinese patent application filed on September 4, 2024, application number 202411238359.2, entitled "Image Sensor and Method for Fabrication Thereof, Camera Module, Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of imaging technology, and in particular to an image sensor and its fabrication method, a camera module, and an electronic device. Background Technology

[0003] An image sensor is a device that converts optical images into electronic signals and is widely used in electronic devices such as digital cameras and mobile phones. In recent years, image sensors have evolved from charge-coupled device (CCD) image sensors to complementary metal-oxide-semiconductor (CMOS) image sensors, which are less expensive and have effectively improved noise levels.

[0004] CMOS image sensors use photoelectric conversion elements to convert light signals into electrical signals. However, these elements cannot distinguish the frequency of light (i.e., the color of light). Therefore, color filters are typically placed on the photoelectric conversion elements to obtain color images. However, color filters filter the light, allowing only a portion of the light to reach the photoelectric conversion element and be converted into an electrical signal, resulting in low light utilization. Therefore, improving the light utilization rate of CMOS image sensors has become a pressing technical problem. Summary of the Invention

[0005] This application provides an image sensor and its fabrication method, a camera module, and an electronic device to enhance the light utilization rate of the image sensor.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, a method for fabricating an image sensor is provided, enabling the integration of an image sensor and a metasurface structure in a low-temperature environment. The method includes: forming an initial image sensor; the initial image sensor includes a stacked circuit layer, a photosensitive layer, and a filter array layer. Using a silicon-containing gas and an oxygen-containing gas, an isolation dielectric layer is formed on the filter array layer under a preset temperature range, a preset pressure range, and a first preset radio frequency power; the isolation dielectric layer covers the filter array layer, and the refractive index of the isolation dielectric layer is in the range of 1.4-1.8. Using a silicon-containing gas and a nitrogen-containing gas, a dielectric thin film is formed on the isolation dielectric layer under a preset temperature range, a preset pressure range, and a second preset radio frequency power; the refractive index of the dielectric thin film is greater than or equal to 1.8. The dielectric thin film is etched to form a metasurface array layer; the metasurface array layer is configured to disperse light incident on it and transmit the dispersed light to the filter array layer. The silicon-containing gas includes an inert gas, and the maximum value of the preset temperature range is less than 230°C.

[0008] The image sensor fabrication method provided in some embodiments of this application forms a dielectric thin film on an initial image sensor including a filter array layer under a preset temperature range, a preset pressure range, and a second preset radio frequency power. This increases the ionization ratio of silicon-containing gas, resulting in a refractive index of the formed dielectric thin film greater than or equal to 1.8. The dielectric thin film is then etched to form a metasurface array layer. This method not only achieves good deposition of the dielectric thin film at a low temperature below 230°C, protecting each color filter in the filter array layer while ensuring good optical properties of the dielectric thin film, enabling the metasurface array layer to have strong dispersion characteristics to meet design requirements, but also improves the light intake and light utilization rate of the fabricated image sensor by utilizing the metasurface array layer to better eliminate optical crosstalk.

[0009] Moreover, by forming an isolation dielectric layer before forming the dielectric thin film, not only can the metasurface array layer and the filter array layer be separated, providing a certain optical path for the light scattered by the metasurface array layer, but the isolation dielectric layer can also cover the metal structure formed before it (such as the metal grid in the filter array), reducing metal contamination, facilitating secondary line entry, and etching to form the metasurface array layer.

[0010] In the first possible design approach, the maximum value of the aforementioned preset temperature range is 200°C. By setting a certain difference between the maximum value of the preset temperature range and the maximum operating temperature of the filter array layer (i.e., 230°C), it is possible to avoid significant adverse effects on the refractive index of the dielectric film while effectively protecting the color filters in the filter array layer.

[0011] In the first possible design approach, the maximum value of the aforementioned preset pressure range is 1000 mTorr. This reduces the total amount of gas remaining in the vacuum reaction chamber, resulting in more concentrated plasma energy and reducing the generation of defects in the isolation dielectric layer and dielectric film, effectively reducing the roughness of the isolation dielectric layer and dielectric film.

[0012] In the first possible design approach, the preset pressure range is 500 mTorr-1000 mTorr. This can more effectively reduce the total amount of gas remaining in the vacuum reaction chamber, making the plasma energy more concentrated, and greatly reducing the generation of defects in the isolation dielectric layer and dielectric film, thus significantly reducing the roughness of the isolation dielectric layer and dielectric film.

[0013] In one possible design approach, the aforementioned first preset radio frequency power is a high-frequency power, greater than or equal to 20W and less than or equal to 100W. This enhances plasma energy, allowing more silicon elements in the silicon-containing gas to participate in the reaction process.

[0014] In one possible design approach, the aforementioned second preset radio frequency power includes high-frequency power and low-frequency power. Specifically, the high-frequency power of the second preset radio frequency power is greater than or equal to 20W and less than or equal to 70W; the low-frequency power of the second preset radio frequency power is greater than or equal to 10W and less than or equal to 50W. This enhances plasma energy, allowing more silicon elements in the silicon-containing gas to participate in the reaction process, thereby increasing the refractive index of the dielectric thin film.

[0015] In one possible design approach, during the formation of the isolation medium layer, the flow ratio of the silicon-containing gas to the oxygen-containing gas ranges from 1:5 to 5:4. Optionally, the flow ratio of the silicon-containing gas to the oxygen-containing gas can be 1:5, 1:4, 1:3, 1:2, 1:1, or 5:4, etc.

[0016] In the first possible design approach, the flow rate of the silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow rate of the oxygen-containing gas ranges from 400 sccm to 1000 sccm.

[0017] Furthermore, in the possible design of the first aspect, the flow rate of the silicon-containing gas ranges from 200 sccm to 400 sccm, and the flow rate of the oxygen-containing gas ranges from 500 sccm to 800 sccm.

[0018] In one possible design approach, during the formation of the dielectric thin film, the flow ratio of the silicon-containing gas to the nitrogen-containing gas ranges from 1:5 to 5:4. Optionally, the flow ratio of the silicon-containing gas to the nitrogen-containing gas can be 1:5, 1:4, 1:3, 1:2, 1:1, or 5:4, etc.

[0019] In the first possible design approach, the flow rate of silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow rate of nitrogen-containing gas ranges from 400 sccm to 1000 sccm.

[0020] Furthermore, in the possible design of the first aspect, the flow rate of the silicon-containing gas ranges from 200 sccm to 400 sccm, and the flow rate of the nitrogen-containing gas ranges from 500 sccm to 800 sccm.

[0021] In the first aspect of possible design, the silicon-containing gas also includes silane, with the silane accounting for a volume percentage ranging from 3% to 10%; the oxygen-containing gas includes nitrous oxide; and the nitrogen-containing gas includes ammonia.

[0022] In the first possible design approach, the thickness of the insulating dielectric layer ranges from 1 μm to 4 μm. This ensures that the insulating dielectric layer provides sufficient optical path, allowing each color filter in the filter array layer to accurately receive light of its corresponding color. It also ensures that the insulating dielectric layer effectively covers the trace metal (or metal structure) beneath it, effectively reducing trace metal contamination.

[0023] In the first possible design approach, the thickness of the dielectric film ranges from 500 nm to 1000 nm. This ensures that the thickness of the metasurface array layer formed by subsequent etching meets the design requirements, thereby exhibiting strong dispersion characteristics (or large dispersion effect), which effectively improves the light intake and light utilization of the fabricated image sensor.

[0024] In the first possible design approach, the roughness of the dielectric film is less than or equal to 5 nm. This ensures that the dielectric film has a high degree of density, fewer defects, and reduced light loss.

[0025] In a second aspect, an image sensor is provided, which is fabricated using a method described in any of the design embodiments of the first aspect. The image sensor includes: an initial image sensor, an isolation dielectric layer, and a metasurface array layer. The initial image sensor includes a stacked circuit layer, a photosensitive layer, and a filter array layer. The isolation dielectric layer is located on and covers the filter array layer. The refractive index of the isolation dielectric layer is in the range of 1.4-1.8. The metasurface array layer is located on the isolation dielectric layer, and the refractive index of the metasurface array layer is greater than or equal to 1.8. The metasurface array layer is configured to disperse light incident on it and transmit the dispersed light to the filter array layer.

[0026] In the second possible design approach, the thickness of the isolation dielectric layer ranges from 1 μm to 4 μm, and the thickness of the metasurface array layer ranges from 500 nm to 1000 nm.

[0027] In the second possible design approach, the roughness of the surface of the metasurface array layer on the side away from the isolation dielectric layer is less than or equal to 5 nm.

[0028] Thirdly, a camera module is provided, comprising an image sensor and a lens assembly as described in any of the designs in the second aspect. The lens assembly is located on the light-incident side of the image sensor.

[0029] Fourthly, an electronic device is provided, comprising: a camera module and a processor as described in any of the designs in the third aspect. The processor is electrically connected to an image sensor in the camera module.

[0030] The technical effects of any of the design methods in the second to fourth aspects can be found in the technical effects of different design methods in the first aspect, and will not be repeated here. Attached Figure Description

[0031] Figure 1 is an architectural diagram of an electronic device provided in an embodiment of this application;

[0032] Figure 2 is a structural diagram of an electronic device provided in an embodiment of this application;

[0033] Figure 3 is an exploded view of a camera module provided in an embodiment of this application;

[0034] Figure 4 is a structural diagram of an initial image sensor provided in an embodiment of this application;

[0035] Figure 5 is a flowchart of a method for fabricating an image sensor according to an embodiment of this application;

[0036] Figure 6 is a structural diagram of an initial image sensor and a vacuum reaction chamber provided in an embodiment of this application;

[0037] Figures 7a-7f are structural diagrams corresponding to each step in a method for fabricating an image sensor according to an embodiment of this application;

[0038] Figure 8 is a structural diagram of an image sensor provided in an embodiment of this application;

[0039] Figure 9 is a perspective view of an image sensor provided in an embodiment of this application;

[0040] Figure 10 is a structural diagram of a color pixel unit of an image sensor provided in an embodiment of this application;

[0041] Figure 11 is a graph showing the refractive index of an isolation dielectric layer at different light wavelengths according to an embodiment of this application;

[0042] Figure 12 is a graph showing the refractive index and extinction coefficient of a dielectric thin film at different light wavelengths according to an embodiment of this application. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0044] In the description of this application, unless otherwise stated, "multiple" means two or more. "At least one" or similar expressions refer to any combination of these items, including any combination of a single or multiple items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0045] Furthermore, to facilitate a clear description of the technical solutions in the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that "first" and "second" are not necessarily different. Meanwhile, in the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is being used as an example, illustration, or description. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of terms such as "exemplary" or "for example" is intended to present related concepts in a concrete manner for ease of understanding.

[0046] In the embodiments of this application, unless otherwise expressly specified and limited, the term "connection" can refer to a direct mechanical connection or an electrical connection, or an indirect mechanical connection or electrical connection via an intermediate medium. The mechanical connection here is not limited to whether it is used for transmitting electrical signals, while the electrical connection is used for transmitting electrical signals.

[0047] This application describes exemplary embodiments with reference to cross-sectional views and / or plan views as idealized exemplary drawings. In the drawings, the thickness of layers and regions is enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as limited to the shapes of the regions shown in this application, but rather include shape deviations due to, for example, manufacturing processes. For example, etched regions shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments.

[0048] Furthermore, the architecture and scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the evolution of architecture and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0049] Some embodiments of this application provide an electronic device that can be applied in fields such as security, photography and videography, automotive electronics, or industrial machine vision. This electronic device may include a handheld device, an in-vehicle device, a wearable device, a computing device, or other processing devices connected to a wireless modem.

[0050] For example, the electronic devices in the embodiments of this application may be digital cameras, cellular phones, smartphones, personal digital assistant (PDA) computers, tablet computers, laptop computers, machine type communication (MTC) terminals, point of sale (POS) terminals, in-vehicle computers, head-mounted devices, wearable devices (such as wristbands, smartwatches, etc.), security equipment, virtual reality (VR) devices, augmented reality (AR) devices, and other electronic devices with imaging functions.

[0051] Figure 1 is an architectural diagram of an electronic device provided in an embodiment of this application. As shown in Figure 1, the electronic device 1000 may include a camera module 100 and a processor 200 electrically connected. The camera module 100 includes a lens assembly 110 and an image sensor 120. The camera module 100 is electrically connected to the processor 200, for example, through the image sensor 120.

[0052] The image sensor 120 described above can also be referred to as a photosensitive chip, photosensitive element, etc. For example, the image sensor 120 may include hundreds of thousands to millions of photoelectric conversion elements, which generate electrical charges when exposed to light, that is, they can convert light signals into electrical signals.

[0053] The processor 200 may include an analog-to-digital (A / D) converter 210 and a digital signal processor 220. The A / D converter 210 is an analog-to-digital signal converter used to convert analog electrical signals into digital electrical signals.

[0054] During the shooting process by the electronic device 1000, the light reflected from the subject (also known as the light signal) can be focused onto the image sensor 120 through the lens assembly 110. The image sensor 120 can convert the light signal into an analog electrical signal and transmit it to the processor 200. The analog-to-digital converter 210 in the processor 200 can receive the analog electrical signal, convert it into a digital electrical signal, and transmit it to the digital signal processor 220. The digital signal processor 220 can process the digital electrical signal, for example, by optimizing the data electrical signal through a series of complex mathematical algorithms, and finally output an image.

[0055] Optionally, the processor 200 may also include an analog signal preprocessor 230, which is used to preprocess the analog electrical signals transmitted by the image sensor 120 and then output them to the analog-to-digital converter 210.

[0056] For ease of explanation, the following example uses a mobile phone as an example, which should not be considered a specific limitation on the structure of the electronic device. Figure 2 is a structural diagram of an electronic device provided in an embodiment of this application, wherein (a) in Figure 2 is a front view of the electronic device, and (b) in Figure 2 is a bottom view of the electronic device. Those skilled in the art will understand that the architecture of the electronic device shown in Figure 2 does not constitute a limitation on the electronic device. The electronic device may include more or fewer components than those shown in Figure 2, or may combine some of the components shown in Figure 2, or may have a different arrangement than those shown in Figure 2.

[0057] In some examples, referring to Figures 2(a) and (b), the electronic device 1000 includes a housing 300 and a display screen 400. The housing 300 may include a mid-frame 310 and a rear cover 320, with the display screen 400 and the rear cover 320 respectively mounted on opposite sides of the mid-frame 310.

[0058] The display screen 400 is used to display images, and of course, the display screen 400 can also integrate touch functionality. Optionally, the display screen 400 can be a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, a quantum dot light-emitting diode (QLED) display, a mini light-emitting diode (Mini LED) display, or a micro light-emitting diode (Micro LED) display, etc.

[0059] The aforementioned mid-frame 310 includes a support plate and a border 311 surrounding the support plate. In some examples, referring to Figures 2(a) and (b), the electronic device 1000 also includes devices such as a front-facing camera assembly 500, a rear-facing camera assembly 600, a motherboard 700, a processor 200, a memory 800, and a battery 900 disposed on the support plate.

[0060] As shown in Figure 2(a), a front camera aperture is provided in the display screen 400. The aforementioned front camera assembly 500 is located, for example, between the display screen 400 and the carrier plate, and a portion of the front camera assembly 500 is exposed by the front camera aperture. External light can enter the front camera assembly 500 through the front camera aperture and be captured by the front camera assembly 500.

[0061] As shown in Figure 2(b), at least one rear camera hole is provided in the rear cover 320. The rear camera assembly 600 is located, for example, on the side of the carrier plate away from the display screen 400. For example, the rear camera assembly 600 is entirely located between the carrier plate and the rear cover 320, with the rear camera hole exposing a portion of the rear camera assembly 600; external light can enter the rear camera assembly 600 through the rear camera hole and be captured by the rear camera assembly 600. Alternatively, a portion of the rear camera assembly 600 is located between the carrier plate and the rear cover 320, while another portion extends out of the housing 300 after passing through the rear camera hole; external light can directly enter the rear camera assembly 600 and be captured by the rear camera assembly 600.

[0062] Optionally, the rear camera assembly 600 may include, for example, at least one camera module 610, which may be, for example, a standard camera module, a telephoto camera module, a wide-angle camera module, an ultra-telephoto camera module, or an ultra-wide-angle camera module. Further, the rear camera assembly 600 may also include, for example, a flash module 620.

[0063] The aforementioned motherboard 700 is disposed between the carrier plate and the rear cover 320, and the processor 200 and memory 800 are fixed on the motherboard 700. The aforementioned display screen 400, front-facing camera assembly 500, and rear-facing camera assembly 600 are, for example, coupled to the processor 200. The memory 800 is used to store computer program code, which includes computer instructions. The processor 200 is used to invoke the computer instructions to cause the electronic device 1000 to perform corresponding operations, such as causing the display screen 400 to display a target image, or causing the front-facing camera assembly 500 and the rear-facing camera assembly 600 to acquire a target image.

[0064] The aforementioned battery 900 is disposed between the carrier plate and the rear cover 320 and is electrically connected to the motherboard 700 to supply power to the electronic device 1000.

[0065] In some examples, the electronic device 1000 may also include one or more functional modules such as an antenna module, a mobile communication module, a sensor module, a motor, a microphone module, and a speaker module, which may be electrically connected to the processor 200 to transmit signals.

[0066] Some embodiments of this application also provide a camera module that can be applied to the aforementioned electronic device. In some examples, the camera module can serve as the front-facing camera assembly 500 shown in FIG. 2(a), or as the camera module 610 of the rear-facing camera assembly 600 shown in FIG. 2(b). The embodiments of this application do not limit the application scenarios of the aforementioned camera module.

[0067] Figure 3 is an exploded view of a camera module provided in an embodiment of this application. In some examples, as shown in Figure 3, the camera module 100 includes a lens assembly 110 and an image sensor 120, with the lens assembly 110 located on the light-incident side of the image sensor 120. Here, the light-incident side refers to the side of the image sensor 120 that receives light. The light collected by the lens assembly 110 can be transmitted to the image sensor 120. For example, the optical axis of the lens assembly 110 and the optical axis of the image sensor 120 can coincide.

[0068] Referring again to Figure 3, the camera module 100 may also include: an image sensor driving module 130, a lens driving module 140, an adhesive layer 150, an optical element 160, and a circuit board 170.

[0069] The image sensor 120 can be mounted on the image sensor driving module 130, which can drive the image sensor 120 to move. The lens driving module 140 is arranged around the lens assembly 110, and can drive the lens assembly 110 to move or tilt axially (i.e., in the direction of the optical axis) to achieve optical image stabilization, optical focusing, and aberration adjustment. The lens driving module 140 can be bonded and fixed to the image sensor driving module 130 using an adhesive layer 150.

[0070] The aforementioned optical element 160 includes, for example, a light filter. The optical element 160 can be located between the image sensor 120 and the lens assembly 110, and is positioned opposite to the image sensor 120. After passing through the lens assembly 110, ambient light can pass through the optical element 160 before entering the image sensor 120. The optical element 160 can filter out stray light from the light passing through the lens assembly 110, making the image captured by the camera module 100 more realistic, thereby improving the quality of the camera module 100.

[0071] The aforementioned circuit board 170 is, for example, a flexible circuit board. One end of the circuit board 170 can be electrically connected to the image sensor driving module 130, and the other end can be electrically connected to the processor 200. The circuit board 170 can transmit the electrical signals converted by the image sensor 120 to the processor 200 for processing, and finally output an image.

[0072] It is understandable that the image sensor 120 is the core component of the camera module 100, and the performance of the image sensor 120 affects the quality of the final output image.

[0073] Figure 4 is a structural diagram of an image sensor provided in an embodiment of this application. In some examples, as shown in Figure 4, the image sensor 120 includes: a circuit layer 1, a photosensitive layer 2, and a filter array layer 3 stacked together. The photosensitive layer 2 is located between the circuit layer 1 and the filter array layer 3.

[0074] Referring again to Figure 4, the circuit layer 1 described above includes, for example, multiple layers of metal wiring. These multiple layers of metal wiring are used to form logic circuits, including but not limited to amplifier circuits, analog-to-digital converter circuits, and other related processing circuits. Circuit layer 1 can also be referred to as a metal wiring layer.

[0075] The aforementioned photosensitive layer 2 includes, for example, a plurality of photoelectric conversion elements 21, which may be arranged in an array. Each photoelectric conversion element 21 is configured to receive light incident from its surface away from the circuit layer 1 and convert the received light into an electrical signal. Optionally, the photoelectric conversion element 21 may be a photodiode.

[0076] The aforementioned filter array layer 3 includes multiple color filters 31 and metal grids 32. The multiple color filters 31 can be arranged in an array and correspond one-to-one with the multiple photoelectric conversion elements 21; for example, one color filter 31 is located above one photoelectric conversion element 21. The color filters 31 are configured to filter incident light to allow light of a specific color (e.g., red, green, or blue) to pass through. The metal grids 32 are located between any two adjacent color filters 31, separating them. The metal grids 32 are configured to reduce optical crosstalk.

[0077] The light reflected by the object being photographed can be transmitted through the filter array layer 3 to each photoelectric conversion element 21; each photoelectric conversion element 21 converts the received light into an electrical signal, which can then be transmitted to the circuit layer 1; the logic circuit in the circuit layer 1 can process the electrical signal and then provide the processed electrical signal to other devices (such as the aforementioned circuit board 170 and processor 200).

[0078] Understandably, each color filter 31 only allows light of a specific color to pass through, which facilitates each photoelectric conversion element 21 receiving light of that specific color. Multiple photoelectric conversion elements 21 cooperate with each other to obtain a color image. However, it is precisely because of the filtering of light by each color filter 31 that the light transmittance (or energy transmittance) is low, resulting in a large amount of light information not being effectively utilized, thus reducing the light utilization rate.

[0079] Based on this, some embodiments of this application provide an image sensor and a method for fabricating the image sensor. The image sensor can be a CMOS image sensor (CIS) and can be applied to the aforementioned camera module 100. Figure 5 illustrates a flowchart of a method for fabricating an image sensor; Figures 7a-7f respectively illustrate structural diagrams corresponding to each step in the method for fabricating an image sensor. It should be understood that the steps shown in Figure 5 are not exclusive, and other steps can be performed before, after, or between any of the steps shown in Figure 5. Furthermore, some steps can be performed simultaneously or in a different order than that shown in Figure 5.

[0080] The fabrication method of the above-mentioned image sensor is illustrated below with reference to the accompanying drawings. As shown in Figure 5, the fabrication method includes steps S100-S400.

[0081] S100, as shown in Figure 4, forms an initial image sensor 120a. This initial image sensor 120a includes a circuit layer 1, a photosensitive layer 2, and a filter array layer 3 stacked together. For details regarding the circuit layer 1, photosensitive layer 2, and filter array layer 3, please refer to the relevant descriptions above; they will not be repeated here.

[0082] For example, in this embodiment, a plurality of photoelectric conversion elements 21 arranged in an array and an isolation structure is formed in a semiconductor substrate to isolate any two adjacent photoelectric conversion elements 21, thus obtaining a photosensitive layer 2; then a circuit layer 1 is formed on the photosensitive layer 2; subsequently, the semiconductor substrate can be thinned on the side of the photosensitive layer 2 away from the circuit layer 1; then a metal grid 32 and a plurality of color filters 31 can be sequentially formed on the side of the photosensitive layer 2 away from the circuit layer 1, thus obtaining a filter array layer 3; wherein the material of the color filters 31 includes organic materials, and the material of the metal grid 32 includes metallic materials. Of course, the method for preparing the initial image sensor 120a is not limited to this.

[0083] The aforementioned multiple color filters 31 can be combined in various ways and can be selected and set according to actual needs. For example, the aforementioned multiple color filters 31 include multiple red filters, multiple green filters, and multiple blue filters. Alternatively, the aforementioned multiple color filters 31 may include multiple red filters, multiple yellow filters, and multiple blue filters.

[0084] S200, as shown in Figure 7a, uses silicon-containing gas and oxygen-containing gas to form an isolation dielectric layer 4 on the filter array layer 3 under a preset temperature range, a preset pressure range, and a first preset radio frequency power. The isolation dielectric layer 4 is located on the side of the filter array layer 3 away from the circuit layer 1 and covers the filter array layer 3.

[0085] For example, this application embodiment can employ plasma-enhanced chemical vapor deposition (PECVD) to form the aforementioned isolation dielectric layer 4. Specifically, as shown in FIG6, this application embodiment can provide a vacuum reaction chamber, then place the initial image sensor 120a into the vacuum reaction chamber, and introduce silicon-containing gas and oxygen-containing gas into the vacuum reaction chamber through the gas inlet; the silicon-containing gas and oxygen-containing gas undergo a series of chemical and plasma reactions to form a planar solid thin film structure, such as a silicon oxide thin film, on the filter array layer 3, which can constitute the aforementioned isolation dielectric layer 4. As shown in FIG7a, the formed isolation dielectric layer 4 substantially completely covers the color filter 31 and the metal grid 32 in the filter array layer 3. During the formation of the isolation dielectric layer 4, the exhaust gas can be discharged from the outlet under the action of a vacuum pump.

[0086] During the formation of the isolation medium layer 4, the flow ratio of the silicon-containing gas to the oxygen-containing gas ranges from 1:5 to 5:4. Optionally, the flow ratio of the silicon-containing gas to the oxygen-containing gas can be 1:5, 1:4, 1:3, 1:2, 1:1, or 5:4, etc.

[0087] For example, the flow rate of the silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow rate of the oxygen-containing gas ranges from 400 sccm to 1000 sccm. Optionally, the flow rate range of the silicon-containing gas can be 200 sccm-400 sccm, 200 sccm-350 sccm, 250 sccm-500 sccm, 300 sccm-500 sccm, or 300 sccm-400 sccm, etc., and the flow rate range of the oxygen-containing gas can be 400 sccm-900 sccm, 500 sccm-900 sccm, 500 sccm-800 sccm, 400 sccm-700 sccm, 500 sccm-600 sccm, or 600 sccm-1000 sccm, etc. For example, the flow rate of silicon-containing gas can be 200 sccm, 260 sccm, 310 sccm, 380 sccm, 420 sccm or 500 sccm, etc., and the flow rate of oxygen-containing gas can be 450 sccm, 530 sccm, 590 sccm, 620 sccm, 750 sccm or 1000 sccm, etc.

[0088] This ensures that the silicon-containing gas and oxygen-containing gas in the vacuum reaction chamber are within a reasonable ratio range, allowing more silicon (Si) elements to participate in the reaction.

[0089] The aforementioned silicon-containing gas includes inert gases, including but not limited to argon (Ar). Further, the aforementioned silicon-containing gas also includes silane (SiH4). The volume percentage of silane ranges from 3% to 10%. Optionally, the volume percentage of silane can be 3%, 4%, 5%, 8%, 9%, or 10%. By adding an inert gas to the silicon-containing gas, which is equivalent to adding a diluent gas, the proportion of silane in the silicon-containing gas can be reduced, that is, the proportion of silicon can be reduced. The aforementioned oxygen-containing gas includes, for example, nitrous oxide (N2O). Silane and nitrous oxide can be ionized in a vacuum reaction chamber and a silicon oxide thin film (i.e., the isolation dielectric layer 4) can be formed on the filter array layer 3.

[0090] The temperature and pressure within the vacuum reaction chamber are maintained within a preset temperature range and a preset pressure range, respectively. A high-frequency radio frequency (RF) source is connected, and the RF power is a first preset RF power.

[0091] Understandably, since the material of the color filter 31 includes organic materials, and organic materials have an upper limit to their temperature resistance, the operating temperature of the filter array layer 3 also has an upper limit. The maximum temperature that the color filter 31 can withstand (for example, around 230°C) is equivalent to the maximum operating temperature of the filter array layer 3. Exceeding this maximum operating temperature will cause adverse changes in the optical performance and structural stability of the color filter 31; for example, the color filter 31 may soften, resulting in irreversible damage.

[0092] Therefore, the maximum value of the aforementioned preset temperature range is less than the maximum operating temperature of the filter array layer 3. For example, the maximum value of the aforementioned preset temperature range is less than 230°C. This ensures that the color filter 31 in the filter array layer 3 has good optical performance and structural stability, and ensures that the color filter 31 can be used normally.

[0093] For example, the first preset radio frequency power is greater than or equal to 20W and less than or equal to 100W. Optionally, the first preset radio frequency power can be 20W, 30W, 50W, 65W, 88W, or 100W, etc. Typically, the radio frequency power for depositing inorganic materials is relatively low. In this embodiment, by increasing the first preset radio frequency power of the high-frequency radio frequency source, the plasma energy can be enhanced, allowing more silicon elements in the silicon-containing gas to participate in the reaction process.

[0094] This application embodiment limits the reaction conditions for preparing the isolation dielectric layer 4, namely, preset temperature, preset pressure, first preset radio frequency power, reaction gas, etc., which can increase the proportion of silicon-containing gas ionization in the vacuum reaction chamber, allowing more silicon elements to participate in the reaction process. It can also reduce the total amount of gas remaining in the vacuum reaction chamber, making the plasma energy more concentrated. This can reduce the generation of defects in the isolation dielectric layer 4 and avoid affecting the refractive index of the isolation dielectric layer 4.

[0095] For example, the refractive index of the isolation dielectric layer 4 ranges from 1.4 to 1.8. Optionally, the refractive index of the isolation dielectric layer 4 can be 1.4, 1.46, 1.48, 1.5, 1.6, 1.7, or 1.8, etc. The lower the refractive index of the isolation dielectric layer 4, the better it can meet the optical characteristic requirements of the image sensor.

[0096] S300, as shown in Figure 7b, using silicon-containing gas and nitrogen-containing gas, a dielectric film 5a is formed on the isolation dielectric layer 4 under the aforementioned preset temperature range, the aforementioned preset pressure range, and the second preset radio frequency power. The dielectric film 5a is located on the side of the isolation dielectric layer 4 away from the circuit layer 1 and covers the isolation dielectric layer 4.

[0097] For example, the embodiments of this application can employ a PECVD process to form the aforementioned dielectric thin film 5a. Specifically, analogous to FIG6, the embodiments of this application can provide a vacuum reaction chamber, and then place the initial image sensor 120a with the isolation dielectric layer 4 formed thereon into the vacuum reaction chamber, and introduce silicon-containing gas and nitrogen-containing gas into the vacuum reaction chamber through the gas inlet; the silicon-containing gas and nitrogen-containing gas undergo a series of chemical reactions and plasma reactions to form a planar solid thin film structure on the isolation dielectric layer 4, such as a silicon nitride (Si3N4) thin film, which can constitute the aforementioned dielectric thin film 5a. As shown in FIG7b, the formed dielectric thin film 5a substantially completely covers the isolation dielectric layer 4. During the formation of the dielectric thin film 5a, the exhaust gas can be discharged from the outlet under the action of a vacuum pump.

[0098] During the formation of the dielectric thin film 5a, the flow ratio of the silicon-containing gas to the nitrogen-containing gas ranges from 1:5 to 5:4. Optionally, the flow ratio of the silicon-containing gas to the nitrogen-containing gas can be 1:5, 1:4, 1:3, 1:2, 1:1, or 5:4, etc.

[0099] For example, the flow rate of the silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow rate of the nitrogen-containing gas ranges from 400 sccm to 1000 sccm. Optionally, the flow rate range of the silicon-containing gas can be 200 sccm-400 sccm, 200 sccm-350 sccm, 250 sccm-500 sccm, 300 sccm-500 sccm, or 300 sccm-400 sccm, etc., and the flow rate range of the nitrogen-containing gas can be 400 sccm-900 sccm, 500 sccm-900 sccm, 500 sccm-800 sccm, 400 sccm-700 sccm, 500 sccm-600 sccm, or 600 sccm-1000 sccm, etc. For example, the flow rate of silicon-containing gas can be 200 sccm, 260 sccm, 310 sccm, 380 sccm, 420 sccm or 500 sccm, etc., and the flow rate of nitrogen-containing gas can be 450 sccm, 530 sccm, 590 sccm, 620 sccm, 750 sccm or 1000 sccm, etc.

[0100] This ensures that the silicon-containing gas and oxygen-containing gas in the vacuum reaction chamber are within a reasonable ratio range, allowing more silicon (Si) elements to participate in the reaction and improve the refractive index of the dielectric thin film 5a.

[0101] For example, the nitrogen-containing gas mentioned above includes ammonia (NH3). Regarding silicon-containing gases, please refer to the relevant description above; it will not be repeated here. The chemical reaction that occurs when the silicon-containing gas and the nitrogen-containing gas form the dielectric thin film 5a is, for example, as shown below: 3SiH4 + 4NH3 → Si3N4 + 12H2.

[0102] The temperature and pressure within the vacuum reaction chamber are maintained within a preset temperature range and a preset pressure range, respectively. A high-frequency radio frequency source and a low-frequency radio frequency source are connected, and the power of both is a second preset radio frequency power.

[0103] For example, the high-frequency power of the second preset radio frequency power is greater than or equal to 20W and less than or equal to 70W. The low-frequency power (LF) of the second preset radio frequency power is greater than or equal to 10W and less than or equal to 50W. Optionally, the high-frequency power of the second preset radio frequency power can be 20W, 30W, 40W, 50W, 60W, or 70W, etc. The low-frequency power of the second preset radio frequency power can be 10W, 20W, 30W, 35W, 40W, or 50W, etc. Typically, the radio frequency power for depositing inorganic materials is relatively low. By increasing the above-mentioned second preset radio frequency power, the plasma energy can be enhanced in this embodiment, allowing more silicon elements in the silicon-containing gas to participate in the reaction process, thereby increasing the refractive index of the dielectric film 5a.

[0104] Optionally, in S300 and S200 above, the vacuum reaction chamber used can be the same vacuum reaction chamber or different vacuum reaction chambers; the actual temperature for preparing the dielectric thin film and the isolation dielectric layer can be the same or different; the actual pressure for preparing the dielectric thin film and the isolation dielectric layer can be the same or different; the power of the high-frequency radio frequency source for preparing the dielectric thin film and the isolation dielectric layer can be the same or different.

[0105] It is understood that the material of the aforementioned dielectric film 5a includes inorganic materials. Typically, the deposition of the dielectric film 5a requires a high-temperature environment (e.g., above 1000°C). To protect the color filter 31, if the dielectric film 5a is deposited at a low temperature (e.g., below 230°C), the initial film formation state of the dielectric film 5a will be poor, its density will be reduced, resulting in higher roughness and a lower refractive index. This makes it difficult to meet the design requirements of the metasurface array layer obtained by subsequent etching, which requires optical properties with a high refractive index.

[0106] This embodiment of the application limits the reaction conditions for preparing the dielectric thin film 5a, namely, preset pressure, second radio frequency power, and reaction gas, which can increase the proportion of silicon-containing gas ionization in the vacuum reaction chamber, allowing more silicon elements to participate in the reaction process. It can also reduce the total amount of gas remaining in the vacuum reaction chamber, making the plasma energy more concentrated. This reduces the generation of defects in the dielectric thin film 5a, resulting in better density, reduced roughness, and increased refractive index. This also achieves good deposition of the dielectric thin film 5a under low-temperature conditions (or with the color filter 31 protected).

[0107] For example, the refractive index of the dielectric film 5a is greater than or equal to 1.8. Optionally, the refractive index of the dielectric film 5a can be 1.8, 1.88, 1.9, 2.1, 2.3, 2.5, or 2.6, etc. Here, there is a difference between the refractive index of the dielectric film 5a and the refractive index of the isolation dielectric layer 4. That is, the refractive index of the dielectric film 5a and the refractive index of the isolation dielectric layer 4 are not both 1.8. Furthermore, the larger the difference between the refractive index of the dielectric film 5a and the refractive index of the isolation dielectric layer 4, the better it meets the optical characteristic requirements of the image sensor.

[0108] For example, the roughness of the dielectric film 5a is less than or equal to 5 nm. Optionally, the roughness of the dielectric film 5a can be 3 nm, 3.6 nm, 4 nm, 4.5 nm, 4.7 nm, 5 nm, etc.

[0109] This ensures that the dielectric film 5a has a high degree of density and fewer defects, meeting the design requirements of the metasurface array layer formed by subsequent etching, and effectively improving the light intake and light utilization of the fabricated image sensor.

[0110] S400, as shown in FIG7f, the dielectric thin film 5a is etched to form a metasurface array layer 5. The metasurface array layer 5 is configured to disperse the light incident on the metasurface array layer 5 and transmit the dispersed light to the filter array layer 3.

[0111] For example, in this embodiment, photolithography can be used to etch the dielectric thin film 5a. Specifically, as shown in FIG7c, in this embodiment, a hard mask layer 6a can be formed on the side of the dielectric thin film 5a away from the circuit layer 1, and a photoresist layer 7a can be formed on the side of the hard mask layer 6a away from the circuit layer 1; as shown in FIG7d, the photoresist layer 7a is then exposed and developed to obtain a patterned photoresist layer 7; as shown in FIG7e, the hard mask layer 6a is then etched using the patterned photoresist layer 7 as a mask to obtain a patterned hard mask layer 6; as shown in FIG7f, the dielectric thin film 5a is etched based on the patterned hard mask layer 6 to obtain the metasurface array layer 5. As shown in FIG8 and FIG9, in this embodiment, the patterned photoresist layer 7 and the patterned hard mask layer 6 can also be removed to obtain the image sensor 120.

[0112] The aforementioned metasurface array layer 5 includes multiple nanopillar structures. The orthographic projection shape of these multiple nanopillar structures on the reference plane, as well as the size and arrangement of these multiple nanopillar structures, can be selected and set according to actual needs, and this embodiment does not limit this. The reference plane is perpendicular to the thickness direction of the metasurface array layer 5.

[0113] It is understandable that metal structures (including but not limited to metal grids 32) formed before the dielectric film 5a may lead to excessive trace metal levels, affecting secondary routing and making it difficult to etch the dielectric film 5a. Therefore, in this embodiment, an isolation dielectric layer 4 is formed before forming the dielectric film 5a to cover and shield the aforementioned metal structures (including but not limited to metal grids 32), which can effectively reduce trace metal contamination and avoid affecting secondary routing.

[0114] In this application embodiment, trace metals were tested before and after the formation of the isolation dielectric layer 4. The results are shown in Table 1 below. The “front contamination test” refers to the contamination test of trace metals performed from the side of the filter array layer 3 away from the circuit layer 1, or from the side of the isolation dielectric layer 4 away from the circuit layer 1.

[0115] Table 1

[0116] As shown in Table 1, before the formation of the isolation dielectric layer 4, the contamination of various trace metals generally exceeded the subsequent process standards; however, after the formation of the isolation dielectric layer 4, the contamination of various trace metals was generally reduced to within the subsequent process standards. This means that by forming the isolation dielectric layer 4, the contamination of trace metals can be effectively reduced. This allows for smoother secondary processing, enabling the etching of the dielectric film 5a and the mass production of the image sensor 120. Aluminum is an inherent structure on the initial image sensor 120a and does not affect subsequent secondary processing.

[0117] The metasurface array layer 5 formed by etching the dielectric thin film 5a has strong dispersion characteristics, exhibiting different deflection effects on different colors of light (or different wavelengths of light), thus enabling the directional deflection of different colors of light onto specific color filters 31. During the transmission of these different colors of light to the specific color filters 31, they pass through the insulating dielectric layer 4. The insulating dielectric layer 4 also provides a certain optical path (i.e., a certain transmission distance for the light), facilitating the accurate reception of specific colors of light by different color filters 31.

[0118] Taking the aforementioned multiple color filters 31, including multiple red filters, multiple green filters, and multiple blue filters, as an example. For instance, as shown in Figures 10(a) and (b), the color pixel units in the image sensor are arranged in an RGGB configuration. For example, when external light is incident on the metasurface array layer 5, the multiple nanopillar structures in the metasurface array layer 5 can cooperate with each other to refract the external light, separating red light, green light, and blue light. The red light is transmitted through the isolation medium layer 4, deflected, and transmitted to the red filter; the green light is transmitted through the isolation medium layer 4, deflected, and transmitted to the green filter; and the blue light is transmitted through the isolation medium layer 4, deflected, and transmitted to the blue filter.

[0119] Furthermore, after passing through the corresponding color filter 31, light of different colors can be absorbed by the photoelectric conversion element 21 in the photosensitive layer 2 and converted into electrical signals.

[0120] In this way, compared to setting a separate filter array layer 3, the fabrication method provided in this application combines the initial image sensor 120a and the metasurface array layer 5 to form a "MetaCIS" structure. This allows the large dispersion effect of the fabricated metasurface array layer 5 to deflect light (e.g., red and blue light) that was originally filtered and absorbed by a certain color filter 31 to the corresponding color filter 31. This increases the light intake of the fabricated image sensor, achieves pixel-level spectral dispersion, enhances the light utilization rate of the fabricated image sensor, and improves the signal-to-noise ratio and low-light capability of the electronic device in which the image sensor is applied.

[0121] Therefore, the image sensor fabrication method provided in some embodiments of this application, by forming a dielectric thin film 5a on an initial image sensor 120a including a filter array layer 3, and limiting the formation conditions of the dielectric thin film 5a (e.g., preset pressure, preset radio frequency power, reaction gas, etc.) to increase the ionization ratio of silicon-containing gas in the vacuum reaction chamber, so that the refractive index of the formed dielectric thin film 5a is greater than or equal to 1.8, and then etching the dielectric thin film 5a to form a metasurface array layer 5, not only achieves good deposition of the dielectric thin film 5a in a low-temperature environment below 230°C, but also protects the filter array layer 3 while ensuring good optical properties of the dielectric thin film 5a, so that the metasurface array layer 5 can have strong dispersion characteristics to meet design requirements, and can also improve the light intake and light utilization of the fabricated image sensor by using the metasurface array layer 5 on the basis of better eliminating optical crosstalk using the filter array layer 3.

[0122] Moreover, by forming an isolation dielectric layer 4 before forming the dielectric thin film 5a, not only can the metasurface array layer 5 and the filter array layer 3 be separated, providing a certain optical path for the light scattered by the metasurface array layer 5, but the isolation dielectric layer 4 can also cover the metal structure formed before it, reducing metal contamination and facilitating secondary line entry and etching to form the metasurface array layer 5.

[0123] In some embodiments, the thickness of the isolation medium layer 4 ranges from 1 μm to 4 μm. Optionally, the thickness of the isolation medium layer 4 can be 1 μm, 1.5 μm, 2 μm, 2.8 μm, 3 μm, 3.6 μm, or 4 μm, etc.

[0124] This ensures that the isolation medium layer 4 provides sufficient optical path, allowing each color filter 31 in the filter array layer 3 to accurately receive light of the corresponding color. It also ensures that the isolation medium layer 4 effectively covers the trace metal (or metal structure) below it, effectively reducing trace metal contamination.

[0125] In some embodiments, the thickness of the dielectric film 5a ranges from 500 nm to 1000 nm. Optionally, the thickness of the dielectric film 5a can be 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, etc. Here, the thickness of the dielectric film 5a is essentially not changed during the etching process. Correspondingly, the thickness of the dielectric film 5a is equal to the height of the nanopillars in the subsequently formed metasurface array layer 5.

[0126] This ensures that the thickness of the metasurface array layer 5 formed by subsequent etching meets the design requirements, thereby exhibiting strong dispersion characteristics (or large dispersion effect), which effectively improves the light intake and light utilization of the fabricated image sensor.

[0127] In some examples, the maximum value of the preset temperature range in S200 and S300 above is 200°C. For example, the preset temperature can be 50°C, 80°C, 100°C, 130°C, 150°C, 180°C, or 200°C, etc.

[0128] For example, the minimum value of the preset temperature range is greater than the minimum operating temperature of the filter array layer 3.

[0129] Since the maximum operating temperature of the color filter 31 in the filter array layer 3 may fluctuate to some extent, this embodiment sets a certain difference between the maximum value of the preset temperature range and the maximum operating temperature of the filter array layer 3 (i.e., 230°C). This will not have a significant adverse effect on the refractive index of the dielectric film 5a (or the metasurface array layer 5), and can effectively protect the color filter 31 in the filter array layer 3.

[0130] In some examples, in S200 and S300 above, the maximum value of the preset pressure range is 1000 mTorr. Optionally, the preset pressure can be 400 mTorr, 500 mTorr, 600 mTorr, 700 mTorr, 800 mTorr, 900 mTorr, or 1000 mTorr, etc.

[0131] Typically, the pressure required for depositing inorganic materials is relatively high. In this embodiment, by reducing the preset pressure to a maximum value of 1000 mTorr, the total amount of gas remaining in the vacuum reaction chamber can be reduced, resulting in more concentrated plasma energy and a reduction in defects in the isolation dielectric layer 4 and the dielectric film 5a, effectively reducing the roughness of the isolation dielectric layer 4 and the dielectric film 5a.

[0132] Furthermore, the aforementioned preset pressure range can be, for example, 500 mTorr-1000 mTorr. Optionally, the preset pressure range can be 500 mTorr-950 mTorr, 500 mTorr-750 mTorr, 550 mTorr-900 mTorr, 600 mTorr-850 mTorr, or 650 mTorr-1000 mTorr, etc.

[0133] This can more effectively reduce the total amount of gas remaining in the vacuum reaction chamber, making the plasma energy more concentrated, and greatly reducing the generation of defects in the isolation dielectric layer 4 and the dielectric film 5a, thus greatly reducing the roughness of the isolation dielectric layer 4 and the dielectric film 5a.

[0134] In some embodiments, the present application uses the parameters shown in Table 2 to form an isolation medium layer 4 on the filter array 3, and uses the parameters shown in Table 3 to form a dielectric film 5a on the isolation medium layer 4. The refractive index of the isolation medium layer 4 and the refractive index, extinction coefficient and roughness of the dielectric film 5a are tested respectively.

[0135] Table 2

[0136] Specifically, in this embodiment, the temperature within the vacuum reaction chamber is maintained at 100°C, the preset pressure is maintained within the range of 500 mTorr-1000 mTorr, and the first preset radio frequency power is a high-frequency power maintained within the range of 20W-100W. A silicon-containing gas with a flow rate range of 200 sccm-500 sccm and nitrous oxide with a flow rate range of 400 sccm-1000 sccm are introduced into the vacuum reaction chamber. After a deposition time of 15 minutes, a silicon oxide thin film (i.e., the insulating dielectric layer 4) is obtained. The silicon-containing gas includes silane and argon, and the volume percentage of silane is 5%.

[0137] Table 3

[0138] Specifically, in this embodiment, the temperature within the vacuum reaction chamber is maintained at 200°C, the preset pressure is maintained within the range of 500 mTorr-1000 mTorr, the high-frequency power of the second preset radio frequency power is maintained within the range of 20W-70W, and the low-frequency power of the second preset radio frequency power is maintained within the range of 10W-50W. Silicon-containing gas with a flow rate range of 200 sccm-500 sccm and ammonia gas with a flow rate range of 400 sccm-1000 sccm are introduced into the vacuum reaction chamber. After a deposition time of 45 minutes, a silicon nitride thin film (i.e., dielectric thin film 5a) is obtained. The silicon-containing gas includes silane and argon, and the volume percentage of silane is 5%.

[0139] As shown in Figure 11, the refractive index of the aforementioned insulating dielectric layer 4 remains around 1.47 within the wavelength range of 400nm-760nm, meeting the optical characteristic design requirements. As shown in Figure 12, within the wavelength range of 400nm-760nm, the refractive index of the aforementioned dielectric film 5a ranges from 1.88 to 1.96, with an average refractive index remaining around 1.91; the extinction coefficient of dielectric film 5a is approximately less than 0.015. The roughness of dielectric film 5a is approximately 4.641nm. Dielectric film 5a exhibits a high refractive index, low roughness, and low extinction coefficient, meaning that the dielectric film 5a prepared using the above method has a high degree of density, exhibits minimal loss of incident light, and achieves excellent beam splitting functionality.

[0140] In some embodiments, after removing the patterned photoresist layer 7 and the patterned hard mask layer 6, the present application embodiments may also form structures such as a microlens array layer on the side of the metasurface array layer 5 away from the circuit layer 1.

[0141] Figure 8 is a structural diagram of an image sensor prepared by the preparation method described in any of the above embodiments, and Figure 9 is a perspective view of an image sensor prepared by the preparation method described in any of the above embodiments.

[0142] In some embodiments, as shown in Figures 8 and 9, the image sensor 120 includes an initial image sensor 120a, an isolation dielectric layer 4, and a metasurface array layer 5. The initial image sensor 120a includes a stacked circuit layer 1, a photosensitive layer 2, and a filter array layer 3. For details regarding the circuit layer 1, the photosensitive layer 2, and the filter array layer 3, please refer to the relevant descriptions above; they will not be repeated here.

[0143] Referring again to Figures 8 and 9, the isolation dielectric layer 4 is located on the filter array layer 3. The isolation dielectric layer 4 has a planar structure and covers the filter array layer 3. Specifically, the isolation dielectric layer 4 covers the color filter 31 and the metal grid 32 in the filter array layer 3. For example, the refractive index of the isolation dielectric layer 4 is in the range of 1.4-1.8. Optionally, the refractive index of the isolation dielectric layer 4 can be 1.4, 1.46, 1.48, 1.5, 1.6, 1.7, or 1.8, etc. The lower the refractive index of the isolation dielectric layer 4, the better it meets the optical characteristic requirements of the image sensor 120.

[0144] Referring again to Figures 8 and 9, the metasurface array layer 5 is located on the aforementioned isolation dielectric layer 4. This metasurface array layer 5 may include, for example, multiple nanopillar structures. The orthographic projection shape of these multiple nanopillar structures on the reference plane, as well as the size and arrangement of these multiple nanopillar structures, can be selected and set according to actual needs; this embodiment does not limit these aspects.

[0145] For example, the refractive index of the metasurface array layer 5 is greater than or equal to 1.8. Optionally, the refractive index of the metasurface array layer 5 can be 1.8, 1.88, 1.9, 2.1, 2.3, 2.5, or 2.6, etc. This allows the metasurface array layer 5 to meet the design requirements for beam splitting, enabling it to have beam splitting functionality. Here, there is a difference between the refractive index of the metasurface array layer 5 and the refractive index of the isolation medium layer 4. That is, the refractive index of the metasurface array layer 5 and the refractive index of the isolation medium layer 4 are not both 1.8. Furthermore, the larger the difference between the refractive index of the metasurface array layer 5 and the refractive index of the isolation medium layer 4, the better it meets the optical characteristic requirements of the image sensor 120.

[0146] Furthermore, the aforementioned metasurface array layer 5 is configured to disperse the light incident on the metasurface array layer 5 and transmit the dispersed light to the filter array layer 3.

[0147] Regarding the transmission process of light after it is incident on the metasurface array layer 5, please refer to the relevant explanation above, which will not be repeated here.

[0148] The image sensor 120 provided in some embodiments of this application is fabricated using the fabrication method described in any of the above embodiments. The filter array layer 3 has good structural stability, and the isolation medium layer 4 and metasurface array layer 5 have good optical properties. The embodiments of this application can not only utilize the metasurface array layer 5 to improve the light intake and light utilization of the image sensor 120, and utilize the isolation medium layer 4 to provide a certain optical path for the light scattered by the metasurface array layer 5, but also utilize the filter array layer 3 to better eliminate optical crosstalk.

[0149] In some embodiments, the thickness of the isolation medium layer 4 ranges from 1 μm to 4 μm. Optionally, the thickness of the isolation medium layer 4 can be 1 μm, 1.5 μm, 2 μm, 2.8 μm, 3 μm, 3.6 μm, or 4 μm, etc.

[0150] This ensures that the isolation medium layer 4 provides sufficient optical path, so that each color filter 31 in the filter array layer 3 can accurately receive the light of the corresponding color.

[0151] In some embodiments, the thickness of the metasurface array layer 5 ranges from 500 nm to 1000 nm. Optionally, the thickness of the metasurface array layer 5 can be 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, etc.

[0152] This ensures that the thickness of the metasurface array layer 5 meets the design requirements, thereby enabling it to have strong dispersion characteristics (or large dispersion effect), which effectively improves the light intake and light utilization of the image sensor 120.

[0153] In some embodiments, the roughness of the surface of the metasurface array layer 5 away from the isolation dielectric layer 4 is less than or equal to 5 nm. Optionally, the roughness of the surface of the metasurface array layer 5 away from the isolation dielectric layer 4 can be 3 nm, 3.6 nm, 4 nm, 4.5 nm, 4.7 nm, 5 nm, etc.

[0154] This ensures that the metasurface array layer 5 has a high degree of density and fewer defects, meeting the design requirements for beam splitting and effectively improving the light intake and light utilization of the image sensor 120.

[0155] In addition, the image sensor 120 may also include an anti-reflection structure located between the metasurface array layer 5 and the filter array layer 3, and / or a structure such as a microlens located on the side of the metasurface array layer 5 away from the initial image sensor 120a.

[0156] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed herein should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for fabricating an image sensor, characterized in that, The preparation method includes: An initial image sensor is formed; the initial image sensor includes a stacked circuit layer, a photosensitive layer, and a filter array layer. Using silicon-containing gas and oxygen-containing gas, an isolation medium layer is formed on the filter array layer under a preset temperature range, a preset pressure range, and a first preset radio frequency power; the isolation medium layer covers the filter array layer, and the refractive index of the isolation medium layer is in the range of 1.4-1.8; the maximum value of the preset temperature range is less than 230°C; Using the silicon-containing gas and nitrogen-containing gas, a dielectric thin film is formed on the isolation dielectric layer under the preset temperature range, the preset pressure range, and the second preset radio frequency power; the refractive index of the dielectric thin film is greater than or equal to 1.

8. The dielectric film is etched to form a metasurface array layer; the metasurface array layer is configured to disperse light incident on the metasurface array layer and transmit the dispersed light to the filter array layer.

2. The preparation method according to claim 1, characterized in that, The maximum value of the preset temperature range is 200℃.

3. The preparation method according to claim 1 or 2, characterized in that, The maximum value of the preset pressure range is 1000 mTorr.

4. The preparation method according to claim 3, characterized in that, The preset pressure range is 500mTorr-1000mTorr.

5. The preparation method according to any one of claims 1-4, characterized in that, The first preset radio frequency power is a high-frequency power, and the first preset radio frequency power is greater than or equal to 20W and less than or equal to 100W.

6. The preparation method according to any one of claims 1-5, characterized in that, The second preset radio frequency power includes high-frequency power and low-frequency power; The high-frequency power of the second preset radio frequency power is greater than or equal to 20W and less than or equal to 70W; The low-frequency power of the second preset radio frequency power is greater than or equal to 10W and less than or equal to 50W.

7. The preparation method according to any one of claims 1-6, characterized in that, During the formation of the isolation medium layer, the flow ratio of the silicon-containing gas and the oxygen-containing gas ranges from 1:5 to 5:

4.

8. The preparation method according to claim 7, characterized in that, The flow rate of the silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow rate of the oxygen-containing gas ranges from 400 sccm to 1000 sccm.

9. The preparation method according to claim 8, characterized in that, The flow rate of the silicon-containing gas ranges from 200 sccm to 400 sccm, and the flow rate of the oxygen-containing gas ranges from 500 sccm to 800 sccm.

10. The preparation method according to any one of claims 1-8, characterized in that, During the formation of the dielectric thin film, the flow ratio of the silicon-containing gas to the nitrogen-containing gas ranges from 1:5 to 5:

4.

11. The preparation method according to claim 10, characterized in that, The flow rate of the silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow rate of the nitrogen-containing gas ranges from 400 sccm to 1000 sccm.

12. The preparation method according to claim 11, characterized in that, The flow rate of the silicon-containing gas ranges from 200 sccm to 400 sccm, and the flow rate of the nitrogen-containing gas ranges from 500 sccm to 800 sccm.

13. The preparation method according to any one of claims 1-12, characterized in that, The silicon-containing gas also includes silane, the volume percentage of which is 3%-10%; the oxygen-containing gas includes nitrous oxide; and the nitrogen-containing gas includes ammonia.

14. The preparation method according to any one of claims 1-13, characterized in that, The thickness of the isolation dielectric layer ranges from 1μm to 4μm, and the thickness of the dielectric film ranges from 500nm to 1000nm.

15. The preparation method according to any one of claims 1-14, characterized in that, The roughness of the dielectric film is less than or equal to 5 nm.

16. An image sensor, characterized in that, The image sensor is fabricated using the fabrication method described in any one of claims 1-15; wherein... The image sensor includes: The initial image sensor includes a stacked circuit layer, a photosensitive layer, and a filter array layer; An isolation dielectric layer is located on and covers the filter array layer; the refractive index of the isolation dielectric layer is in the range of 1.4-1.8; and, A metasurface array layer is located on the isolation medium layer; the refractive index of the metasurface array layer is greater than or equal to 1.8; the metasurface array layer is configured to disperse light incident on the metasurface array layer and transmit the dispersed light to the filter array layer.

17. The image sensor according to claim 16, characterized in that, The thickness of the isolation medium layer ranges from 1μm to 4μm, and the thickness of the metasurface array layer ranges from 500nm to 1000nm.

18. The image sensor according to claim 16 or 17, characterized in that, The surface roughness of the metasurface array layer on the side away from the isolation medium layer is less than or equal to 5 nm.

19. A camera module, characterized in that, The camera module includes: The image sensor as described in any one of claims 16-18; and, The lens assembly is located on the light-incident side of the image sensor.

20. An electronic device, characterized in that, The electronic device includes: The camera module as described in claim 19; and, The processor is electrically connected to the image sensor in the camera module.

Images