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 sensor, preparation method thereof, camera module and electronic device

[0001] The present application claims priority to the Chinese patent application No. 202411238359.2, filed on September 4, 2024, entitled "Image sensor, preparation method thereof, camera module and electronic device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of imaging technology, and in particular to an image sensor, a preparation method thereof, a camera module and an electronic device. BACKGROUND

[0003] An image sensor is a device that converts an optical image into an electronic signal, and is widely used in electronic devices such as digital cameras and mobile phones. In recent years, image sensors have developed from charge coupled device (CCD) image sensors to complementary metal oxide semiconductor (CMOS) image sensors, which are lower in cost and have effectively improved noise problems.

[0004] The photoelectric conversion element of a COMS image sensor can convert a light signal into an electrical signal, but the photoelectric conversion element itself cannot distinguish the frequency of light (i.e., cannot distinguish the color of light). Therefore, a color filter is usually provided on the photoelectric conversion element to obtain a color picture. However, the color filter filters light, and only a portion of the light reaches the photoelectric conversion element to be converted into an electrical signal, resulting in low light utilization. Therefore, how to improve the light utilization of the COMS image sensor has become a technical problem to be solved. SUMMARY

[0005] Embodiments of the present application provide an image sensor, a preparation method thereof, a camera module and an electronic device, which are used to enhance the light utilization of the image sensor.

[0006] To achieve the above-mentioned purpose, the embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, a preparation method of an image sensor is provided for realizing the combination of the image sensor and a metasurface structure in a low-temperature environment. The preparation method comprises: forming an initial image sensor; the initial image sensor comprises a circuit layer, a photosensitive layer, and a filter array layer arranged in a stack. An isolation medium layer is formed on the filter array layer by using a silicon-containing gas and an oxygen-containing gas at 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 ranges from 1.4 to 1.8. A medium film is formed on the isolation medium layer by using a silicon-containing gas and a nitrogen-containing gas at a preset temperature range, a preset pressure range, and a second preset radio frequency power; the refractive index of the medium film is greater than or equal to 1.8. The medium 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. The silicon-containing gas comprises an inert gas, and the maximum value of the preset temperature range is less than 230 DEG C.

[0008] The preparation method of the image sensor provided by some embodiments of the present application forms a medium film on the initial image sensor comprising a filter array layer at a preset temperature range, a preset pressure range, and a second preset radio frequency power, so as to increase the ionization ratio of the silicon-containing gas, so that the refractive index of the formed medium film is greater than or equal to 1.8, and then the medium film is etched to form a metasurface array layer, which not only realizes the good deposition of the medium film in a low-temperature environment below 230 DEG C, but also protects the color filters in the filter array layer while ensuring the good optical properties of the medium film, so that the metasurface array layer has strong dispersion properties to meet the design requirements, and the light amount and light utilization of the prepared image sensor can be improved by using the metasurface array layer on the basis of better eliminating optical crosstalk by using the filter array layer.

[0009] Moreover, by forming an isolation medium layer before forming the medium film, the metasurface array layer and the filter array layer can be separated, the light scattered by the metasurface array layer can be provided with a certain optical path, and the metal structure (such as the metal grid in the filter array) formed before the isolation medium layer can be covered to reduce metal pollution and facilitate secondary wiring and etching to form the metasurface array layer.

[0010] In a possible design manner of the first aspect, the maximum value of the preset temperature range is 200 DEG C. By setting the maximum value of the preset temperature range and the maximum working temperature (i.e., 230 DEG C) of the filter array layer to have a certain gap, the refractive index of the medium film can be effectively protected without having a large adverse effect on the refractive index of the medium film.

[0011] In a possible design of the first aspect, the maximum value of the preset pressure range is 1000 mTorr. In this way, the total amount of residual gas in the vacuum reaction chamber can be reduced, the plasma energy is more concentrated, and the generation of defects in the isolation dielectric layer and the dielectric film is reduced, thereby effectively reducing the roughness of the isolation dielectric layer and the dielectric film.

[0012] In a possible design of the first aspect, the preset pressure range is 500 mTorr-1000 mTorr. In this way, the total amount of residual gas in the vacuum reaction chamber can be more effectively reduced, the plasma energy is more concentrated, and the generation of defects in the isolation dielectric layer and the dielectric film is greatly reduced, thereby greatly reducing the roughness of the isolation dielectric layer and the dielectric film.

[0013] In a possible design of the first aspect, the first preset RF power is high-frequency power, and the first preset RF power is greater than or equal to 20 W and less than or equal to 100 W. In this way, the plasma energy can be enhanced, so that the silicon element in the silicon-containing gas can participate more in the reaction process.

[0014] In a possible design of the first aspect, the second preset RF power includes high-frequency power and low-frequency power. The high-frequency power of the second preset RF power is greater than or equal to 20 W and less than or equal to 70 W, and the low-frequency power of the second preset RF power is greater than or equal to 10 W and less than or equal to 50 W. In this way, the plasma energy can be enhanced, so that the silicon element in the silicon-containing gas can participate more in the reaction process, thereby improving the refractive index of the dielectric film.

[0015] In a possible design of the first aspect, in the process of forming the isolation dielectric layer, the flow ratio of the silicon-containing gas to the oxygen-containing gas ranges from 1:5 to 5:4. Alternatively, 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 a possible design of the first aspect, the flow of the silicon-containing gas ranges from 200 sccm to 500 sccm, and the flow of the oxygen-containing gas ranges from 400 sccm to 1000 sccm.

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

[0018] In a possible design of the first aspect, in the process of forming the dielectric film, the flow ratio of the silicon-containing gas to the nitrogen-containing gas ranges from 1:5 to 5:4. Alternatively, 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 a possible design of the first aspect, 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.

[0020] Further, in a 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 a possible design of the first aspect, the silicon-containing gas further includes silane, and the volume percentage of the silane ranges from 3% to 10%; the oxygen-containing gas includes laughing gas; and the nitrogen-containing gas includes ammonia.

[0022] In a possible design of the first aspect, the thickness of the isolation medium layer ranges from 1 μm to 4 μm. This can ensure that the isolation medium layer can provide sufficient optical path, so that each color filter in the color filter array layer can accurately receive light of a corresponding color, and can also ensure that the isolation medium layer effectively covers the trace metal (or metal structure) below, effectively reducing the pollution of the trace metal.

[0023] In a possible design of the first aspect, the thickness of the dielectric film ranges from 500 nm to 1000 nm. This can ensure that the thickness of the metasurface array layer formed by subsequent etching can meet the design requirements, and thus the metasurface array layer can have strong dispersion characteristics (or large dispersion effect), so as to effectively improve the light intake and light utilization of the image sensor formed.

[0024] In a possible design of the first aspect, the roughness of the dielectric film is less than or equal to 5 nm. This can ensure that the dielectric film has a high degree of compactness and fewer defects, reducing light loss.

[0025] In a second aspect, an image sensor is provided, which is formed by the preparation method of any of the designs in the first aspect. The image sensor includes an initial image sensor, an isolation medium layer, and a metasurface array layer. The initial image sensor includes a circuit layer, a photosensitive layer, and a color filter array layer arranged in layers. The isolation medium layer is located on the color filter array layer and covers the color filter array layer. The refractive index of the isolation medium layer ranges from 1.4 to 1.8. The metasurface array layer is located on the isolation medium 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 the metasurface array layer and transmit the dispersed light to the color filter array layer.

[0026] In a possible design of the second aspect, the thickness of the isolation medium 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 a possible design of the second aspect, the roughness of the side surface of the metasurface array layer away from the isolation medium layer is less than or equal to 5 nm.

[0028] In a third aspect, a camera module is provided, including the image sensor and the lens assembly according to any of the designs of the second aspect. The lens assembly is located on the light-incident side of the image sensor.

[0029] In a fourth aspect, an electronic device is provided, including the camera module according to any of the designs of the third aspect and a processor. The processor is electrically connected to the image sensor in the camera module.

[0030] The technical effects brought by any of the designs of the second aspect to the fourth aspect can be referred to the technical effects brought by the different designs of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 is an architecture diagram of an electronic device according to an embodiment of the present application;

[0032] FIG. 2 is a structural diagram of an electronic device according to an embodiment of the present application;

[0033] FIG. 3 is an exploded view of a camera module according to an embodiment of the present application;

[0034] FIG. 4 is a structural diagram of an (initial) image sensor according to an embodiment of the present application;

[0035] FIG. 5 is a flowchart of a preparation method of an image sensor according to an embodiment of the present application;

[0036] FIG. 6 is a structural diagram of an initial image sensor and a vacuum reaction cavity according to an embodiment of the present application;

[0037] FIGS. 7a-7f are structural diagrams corresponding to respective steps in a preparation method of an image sensor according to an embodiment of the present application;

[0038] FIG. 8 is a structural diagram of an image sensor according to an embodiment of the present application;

[0039] FIG. 9 is a perspective view of an image sensor according to an embodiment of the present application;

[0040] FIG. 10 is a structural diagram of a color pixel unit of an image sensor according to an embodiment of the present application;

[0041] FIG. 11 is a graph of the refractive index of an isolation medium layer at different wavelengths of light according to an embodiment of the present application;

[0042] FIG. 12 is a graph of the refractive index and extinction coefficient of a medium film at different wavelengths of light according to an embodiment of the present application. DETAILED DESCRIPTION

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

[0044] In the description of the present application, "a plurality of" means two or more than two, unless otherwise specified. "At least one" or similar expressions mean any combination of these items, including any combination of single or multiple. For example, at least one of a, b or c can mean a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0045] In addition, in order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, "first", "second" and the like are used to distinguish the same or similar items with basically the same function and effect. Those skilled in the art can understand that "first", "second" and the like do not limit the quantity and execution order, and "first", "second" and the like do not necessarily mean different. At the same time, in the embodiments of the present application, "exemplary" or "for example" means to serve as an example, illustration or description. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the use of "exemplary" or "for example" is intended to present the relevant concept in a specific manner, and to facilitate understanding.

[0046] In the embodiments of the present application, unless otherwise specified and limited, the term "connection" can be a direct mechanical connection or electrical connection, or an indirect mechanical connection or electrical connection through an intermediate medium. The mechanical connection here can not limit whether it is used to transmit electrical signals, and the electrical connection is used to transmit electrical signals.

[0047] The exemplary embodiments are described herein with reference to cross-sectional and / or plan illustrations that are schematic illustrations of idealized embodiments (and in which the thickness of layers, regions, and / or areas can be exaggerated for clarity). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, the exemplary embodiments should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region illustrated as a rectangle will typically have rounded or curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the exemplary embodiments.

[0048] In addition, the architecture and scenarios described in the embodiments of the present application are for more clearly illustrating the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. It can be known by those skilled in the art that, with the evolution of the architecture and the appearance of new scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0049] Some embodiments of the present application provide an electronic device which can be applied to the fields of security and protection, photography and videography, automotive electronics, or industrial machine vision, etc. The electronic device can include a handheld device, a vehicle-mounted device, a wearable device, a computing device, or other processing devices connected to a wireless modem.

[0050] For example, the electronic device in the embodiments of the present application can be a digital camera, a cellular phone, a smart phone, a personal digital assistant (PDA) computer, a tablet computer, a laptop computer, a machine type communication (MTC) terminal, a point of sales (POS), a vehicle-mounted computer, a head-mounted device, a wearable device (such as a bracelet, a smart watch, etc.), a security and protection device, a virtual reality (VR) device, an augmented reality (AR) device, and other electronic devices with imaging functions.

[0051] FIG. 1 is an architecture diagram of an electronic device according to an embodiment of the present application. As shown in FIG. 1, the electronic device 1000 can 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 can also be referred to as a photosensitive chip, a photosensitive element, etc. For example, the image sensor 120 can include hundreds of thousands to millions of photoelectric conversion elements that generate electric charges after receiving light, i.e., can convert optical signals into electrical signals.

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

[0054] During photographing of the electronic device 1000, light (which can also be referred to as an optical signal) reflected by an object can be converged on the image sensor 120 through the lens assembly 110. The image sensor 120 can convert the optical signal into an analog electrical signal and transmit the analog electrical signal to the processor 200. The analog-to-digital converter 210 in the processor 200 can receive the analog electrical signal and convert it into a digital electrical signal, which is transmitted to the digital signal processor 220. The digital signal processor 220 can process the digital electrical signal, for example, by performing a series of complex mathematical algorithm operations to optimize the data electrical signal, and finally output an image.

[0055] Optionally, the processor 200 can further include an analog signal preprocessor 230 configured to pre-process the analog electrical signal transmitted by the image sensor 120 and output the pre-processed analog electrical signal to the analog-to-digital converter 210.

[0056] For the convenience of description, the electronic device is taken as a mobile phone as an example for illustration, which cannot be considered as a specific limitation on the structure of the electronic device. FIG. 2 is a structural diagram of an electronic device according to an embodiment of the present application. As shown in FIG. 2, (a) is a front view of the electronic device, and (b) is a bottom view of the electronic device. Those skilled in the art can understand that the architecture of the electronic device shown in FIG. 2 does not constitute a limitation on the electronic device. The electronic device can include more or fewer components than those shown in FIG. 2, or can combine some of the components shown in FIG. 2, or can be arranged differently from the components shown in FIG. 2.

[0057] In some examples, in combination with (a) and (b) in FIG. 2, the electronic device 1000 includes a housing 300 and a display screen 400. Among them, the housing 300 can include a middle frame 310 and a back cover 320, and the display screen 400 and the back cover 320 are respectively installed on the two opposite sides of the middle frame 310.

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

[0059] The above-mentioned middle frame 310 includes a bearing plate and a frame 311 around the bearing plate. In some examples, in combination with (a) and (b) in FIG. 2, the electronic device 1000 further includes a front camera assembly 500, a rear camera assembly 600, a mainboard 700, a processor 200, a memory 800, and a battery 900, etc. devices arranged on the bearing plate.

[0060] As shown in (a) of FIG. 2, a front camera hole is provided in the display screen 400. The above-mentioned front camera assembly 500 is located between the display screen 400 and the bearing plate, for example, and a part of the front camera assembly 500 is exposed through the front camera hole. External light can be incident on the front camera assembly 500 through the front camera hole and be collected by the front camera assembly 500.

[0061] As shown in (b) of FIG. 2, at least one rear camera hole is provided in the back cover 320. The rear camera assembly 600 is located on the side of the bearing plate away from the display screen 400, for example. For example, the rear camera assembly 600 is located between the bearing plate and the back cover 320 as a whole, and a part of the rear camera assembly 600 is exposed through the rear camera hole; external light can be incident on the rear camera assembly 600 through the rear camera hole and be collected by the rear camera assembly 600. For another example, a part of the rear camera assembly 600 is located between the bearing plate and the back cover 320, and the other part extends out of the housing 300 through the rear camera hole; external light can be directly incident on the rear camera assembly 600 and be collected by the rear camera assembly 600.

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

[0063] The mainboard 700 is disposed between the bearing plate and the rear cover 320, and the processor 200 and the memory 800 are fixed on the mainboard 700. The display screen 400, the front camera assembly 500, and the rear camera assembly 600 are coupled to the processor 200, for example. The memory 800 is configured to store computer program code including computer instructions. The processor 200 is configured to invoke the computer instructions to cause the electronic device 1000 to perform corresponding operations, for example, causing the display screen 400 to display a target image, causing the front camera assembly 500 and the rear camera assembly 600 to capture the target image, and the like.

[0064] The battery 900 is disposed between the bearing plate and the rear cover 320 and is electrically connected to the mainboard 700, and is configured to supply power to the electronic device 1000.

[0065] In some examples, the electronic device 1000 can further include one or more of an antenna module, a mobile communication module, a sensor module, a motor, a microphone module, a loudspeaker module, and the like. These functional modules can be electrically connected to the processor 200 to transmit signals.

[0066] Some embodiments of the present application also provide a camera module, which can be applied to the electronic device described above. In some examples, the camera module can be used as the front camera assembly 500 shown in (a) of FIG. 2, or as the camera module 610 of the rear camera assembly 600 shown in (b) of FIG. 2. The application scenarios of the camera module described above are not limited by the embodiments of the present application.

[0067] FIG. 3 is an exploded view of a camera module according to an embodiment of the present application. In some examples, as shown in FIG. 3, the camera module 100 includes a lens assembly 110 and an image sensor 120, and the lens assembly 110 is located on the light-receiving side of the image sensor 120. Here, the light-receiving 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] Continuing to refer to FIG. 3, the camera module 100 can further 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 disposed on an image sensor driving module 130, and the image sensor driving module 130 can drive the image sensor 120 to move. The lens driving module 140 is annularly disposed on the lens assembly 110, and the lens driving module 140 can drive the lens assembly 110 to move or tilt in the axial direction (i.e., the extension direction of the optical axis) to achieve optical image stabilization, optical focusing, aberration adjustment, and the like. The lens driving module 140 can be fixed to the image sensor driving module 130 by means of an adhesive layer 150.

[0070] The optical element 160, for example, includes a filter. The optical element 160 can be disposed between the image sensor 120 and the lens assembly 110 and opposite the image sensor 120. External light passing through the lens assembly 110 can be incident on the image sensor 120 after passing through the optical element 160. The optical element 160 can filter stray light in the light passing through the lens assembly 110, so that the image captured by the camera module 100 is more realistic, thereby improving the quality of the camera module 100.

[0071] The circuit board 170, for example, is 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 signal converted by the image sensor 120 to the processor 200 for processing, and finally output an image.

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

[0073] FIG. 4 is a structural diagram of an image sensor according to an embodiment of the present application. In some examples, as shown in FIG. 4, the image sensor 120 includes a circuit layer 1, a photosensitive layer 2, and a filter array layer 3 which are stacked. The photosensitive layer 2 is located between the circuit layer 1 and the filter array layer 3.

[0074] Referring back to FIG. 4, the circuit layer 1, for example, includes a plurality of metal wiring layers, which are used to form a logic circuit, including but not limited to an amplification circuit, an analog-to-digital conversion circuit, other related processing circuits, and the like. The circuit layer 1 can also be referred to as a metal wiring layer.

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

[0076] The filter array layer 3 includes a plurality of color filters 31 and metal grids 32. The plurality of color filters 31 can be arranged in an array and correspond to the plurality of photoelectric conversion elements 21 one by one; for example, one color filter 31 is located above one photoelectric conversion element 21. The color filter 31 is configured to filter the incident light so that light of a specific color (for example, red, green or blue) can pass through. The metal grid 32 is located between any two adjacent color filters 31 to separate the two adjacent color filters 31. The metal grid 32 is configured to reduce optical cross-talk.

[0077] The light reflected by the object can be transmitted to the photoelectric conversion elements 21 through the filter array layer 3; the photoelectric conversion elements 21 can convert the received light into an electrical signal and transmit the electrical signal 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 (for example, the circuit board 170 and the processor 200).

[0078] It can be understood that each color filter 31 only allows light of a specific color to pass through, which facilitates each photoelectric conversion element 21 to receive light of a specific color, and the plurality of photoelectric conversion elements 21 cooperate with each other to obtain a color image. However, due to the filtering of the color filters 31, the transmittance of light (or the transmittance of energy) is low, resulting in a large amount of light information not being effectively utilized, and reducing the light utilization rate.

[0079] Based on this, some embodiments of the present application provide an image sensor and a preparation method for preparing the image sensor. The image sensor can be a CMOS image sensor (CIS), and can be applied to the camera module 100 described above. Wherein, FIG. 5 shows a flowchart of a preparation method of an image sensor; FIGS. 7a-7f respectively show the structure diagram corresponding to each step in the preparation method of an image sensor. It should be understood that the steps shown in FIG. 5 are not exclusive, and other steps can be performed before, after or between any of the steps shown in FIG. 5. In addition, some of the steps can be performed simultaneously, or can be performed in an order different from that shown in FIG. 5.

[0080] The preparation method of the image sensor is schematically described below with reference to the accompanying drawings. As shown in FIG. 5, the preparation method includes S100-S400.

[0081] S100, as shown in FIG. 4, an initial image sensor 120a is formed. The initial image sensor 120a includes a circuit layer 1, a photosensitive layer 2 and a filter array layer 3 arranged in a stack. As to the circuit layer 1, the photosensitive layer 2 and the filter array layer 3, please refer to the above description and no further elaboration is made here.

[0082] For example, the embodiment of the present application can first form a plurality of photoelectric conversion elements 21 arranged in an array and a separation structure separating any two adjacent photoelectric conversion elements 21 in a semiconductor substrate to obtain the photosensitive layer 2; then form the circuit layer 1 on the photosensitive layer 2; then perform a thinning process on the semiconductor substrate on the side of the photosensitive layer 2 away from the circuit layer 1; then form the metal grid 32 and a plurality of color filters 31 in sequence on the side of the photosensitive layer 2 away from the circuit layer 1 to obtain the filter array layer 3; wherein the material of the color filter 31 includes an organic material and the material of the metal grid 32 includes a metal material. Of course, the method for preparing the initial image sensor 120a is not limited to this.

[0083] The plurality of color filters 31 can have a variety of combinations, which can be selected according to actual needs. For example, the plurality of color filters 31 includes a plurality of red filters, a plurality of green filters and a plurality of blue filters. For another example, the plurality of color filters 31 includes a plurality of red filters, a plurality of yellow filters and a plurality of blue filters.

[0084] S200, as shown in FIG. 7a, a separation dielectric layer 4 is formed on the filter array layer 3 by using a silicon-containing gas and an oxygen-containing gas at a preset temperature range, a preset pressure range and a first preset radio frequency power. The separation 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, the embodiment of the present application can form the separation dielectric layer 4 by using a plasma enhanced chemical vapor deposition (PECVD) process. Specifically, as shown in FIG. 6, a vacuum reaction cavity can be provided, the initial image sensor 120a is placed in the vacuum reaction cavity, and a silicon-containing gas and an oxygen-containing gas are introduced into the vacuum reaction cavity through a gas inlet; the silicon-containing gas and the oxygen-containing gas undergo a series of chemical reactions and plasma reactions to form a solid thin film structure, for example, a silicon oxide film, on the filter array layer 3, which can constitute the separation dielectric layer 4. As shown in FIG. 7a, the separation dielectric layer 4 formed substantially completely covers the color filters 31 and the metal grid 32 in the filter array layer 3. During the formation of the separation dielectric layer 4, the exhaust gas can be discharged from the outlet under the action of a vacuum pump.

[0086] In the process of forming the isolation medium layer 4, the flow ratio of the above-mentioned silicon-containing gas and oxygen-containing gas ranges from 1:5 to 5:4. Alternatively, the flow ratio of the silicon-containing gas and 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 can be 200 sccm, 260 sccm, 310 sccm, 380 sccm, 420 sccm or 500 sccm, etc., and the flow rate of the oxygen-containing gas can be 450 sccm, 530 sccm, 590 sccm, 620 sccm, 750 sccm or 1000 sccm, etc.

[0088] In this way, the silicon-containing gas and oxygen-containing gas in the vacuum reaction chamber can be ensured to be within a reasonable proportion range, so that more silicon (Si) elements can participate in the reaction.

[0089] The above-mentioned silicon-containing gas includes inert gas, which includes but is not limited to argon (Ar). Further, the above-mentioned silicon-containing gas also includes silane (SiH4). The volume percentage of silane ranges from 3% to 10%. Alternatively, the volume percentage of silane can be 3%, 4%, 5%, 8%, 9% or 10%. By increasing the inert gas in the silicon-containing gas, which is equivalent to adding dilution gas, the proportion of silane in the silicon-containing gas can be reduced, i.e., the proportion of silicon can be reduced. The above-mentioned oxygen-containing gas includes, for example, laughing gas (N2O). Silane and laughing gas can be ionized in the vacuum reaction chamber and generate a silicon oxide film (i.e., the isolation medium layer 4) on the filter array layer 3.

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

[0091] It can be understood that, since the material of the color filter 31 includes an organic material, and the temperature that the organic material can withstand has an upper limit, the working temperature of the filter array layer 3 has an upper limit. The maximum temperature that the color filter 31 can withstand (for example, about 230°C) can be equivalent to the maximum working temperature of the filter array layer 3. When the maximum working temperature is exceeded, the optical performance and structural stability of the color filter 31 will change adversely, for example, the color filter 31 becomes soft and causes irreversible damage.

[0092] Based on this, the maximum value of the above-mentioned preset temperature range is less than the maximum working temperature of the filter array layer 3. For example, the maximum value of the above-mentioned preset temperature range is less than 230°C. In this way, it can be ensured that the color filter 31 in the filter array layer 3 has good optical performance and structural stability, and 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. Generally, the radio frequency power for depositing inorganic materials is small. By increasing the first preset radio frequency power of the above-mentioned high-frequency radio frequency source, the present embodiment can enhance the plasma energy, so that more silicon elements in the silicon-containing gas can participate in the reaction process.

[0094] By limiting the reaction conditions for preparing the isolation medium layer 4, that is, the preset temperature, the preset pressure, the first preset radio frequency power, the reaction gas, etc., the present embodiment can increase the ionization ratio of the silicon-containing gas in the vacuum reaction chamber, so that more silicon elements participate in the reaction process, and the total amount of residual gas in the vacuum reaction chamber can be reduced, so that the plasma energy is more concentrated. In this way, the generation of defects in the isolation medium layer 4 can be reduced, and the refractive index of the isolation medium layer 4 can be avoided.

[0095] For example, the refractive index of the isolation medium layer 4 is in the range of 1.4-1.8. Optionally, the refractive index of the isolation medium layer 4 can be 1.4, 1.46, 1.48, 1.5, 1.6, 1.7 or 1.8, etc. The smaller the refractive index of the isolation medium layer 4, the better the optical performance of the image sensor can be met.

[0096] S300, as shown in FIG. 7b, a silicon-containing gas and a nitrogen-containing gas are used to form a dielectric film 5a on the isolation medium layer 4 under the above-mentioned preset temperature range, the above-mentioned preset pressure range and the second preset radio frequency power. The dielectric film 5a is located on the side of the isolation medium layer 4 away from the circuit layer 1 and covers the isolation medium layer 4.

[0097] For example, the embodiment of the present application can form the dielectric film 5a by using a PECVD process. Specifically, similar to the process shown in FIG. 6, the embodiment of the present application can provide a vacuum reaction chamber, and then put the initial image sensor 120a formed with the isolation dielectric layer 4 into the vacuum reaction chamber, and then introduce a silicon-containing gas and a nitrogen-containing gas into the vacuum reaction chamber through a gas inlet. The silicon-containing gas and the nitrogen-containing gas can form a planar solid film structure on the isolation dielectric layer 4 by a series of chemical reactions and plasma reactions, for example, a silicon nitride (Si3N4) film, which can constitute the dielectric film 5a. As shown in FIG. 7b, the dielectric film 5a formed can substantially completely cover the isolation dielectric layer 4. During the formation of the dielectric film 5a, the exhaust gas can be discharged from the outlet under the action of the vacuum pump.

[0098] During the formation of the dielectric film 5a, the flow ratio of the silicon-containing gas and the nitrogen-containing gas can be in the range of 1:5-5:4. Alternatively, the flow ratio of the silicon-containing gas and 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 can be in the range of 200-500 sccm, and the flow rate of the nitrogen-containing gas can be in the range of 400-1000 sccm. Alternatively, the flow rate of the silicon-containing gas can be in the range of 200-400 sccm, 200-350 sccm, 250-500 sccm, 300-500 sccm or 300-400 sccm, etc., and the flow rate of the nitrogen-containing gas can be in the range of 400-900 sccm, 500-900 sccm, 500-800 sccm, 400-700 sccm, 500-600 sccm or 600-1000 sccm, etc. For example, the flow rate of the silicon-containing gas can be 200 sccm, 260 sccm, 310 sccm, 380 sccm, 420 sccm or 500 sccm, etc., and the flow rate of the nitrogen-containing gas can be 450 sccm, 530 sccm, 590 sccm, 620 sccm, 750 sccm or 1000 sccm, etc.

[0100] In this way, the silicon-containing gas and the nitrogen-containing gas in the vacuum reaction chamber can be in a relatively reasonable proportion, so that more silicon (Si) elements can participate in the reaction, and the refractive index of the dielectric film 5a can be improved.

[0101] Exemplarily, the nitrogen-containing gas includes ammonia (NH3). As to the silicon-containing gas, refer to the relevant description above, which will not be repeated here. The silicon-containing gas and the nitrogen-containing gas form a chemical reaction, for example, as shown below: 3SiH4+4NH3→Si3N4+12H2.

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

[0103] Exemplarily, 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. Generally, the radio frequency power for depositing inorganic materials is small. By increasing the second preset radio frequency power, the plasma energy can be enhanced, so that the silicon element in the silicon-containing gas can participate more in the reaction process, thereby improving the refractive index of the dielectric thin film 5a.

[0104] Optionally, in the S300 and the S200, the vacuum reaction chambers used can be the same vacuum reaction chamber or different vacuum reaction chambers; the actual temperatures for preparing the dielectric thin film and the isolation dielectric layer can be the same or different; the actual pressures for preparing the dielectric thin film and the isolation dielectric layer can be the same or different; and the powers of the high-frequency radio frequency sources for preparing the dielectric thin film and the isolation dielectric layer can be the same or different.

[0105] It can be understood that the material of the dielectric thin film 5a includes inorganic material. Generally, the deposition of the dielectric thin film 5a needs to be carried out in a high-temperature environment (for example, greater than 1000°C). In order to protect the color filter 31, if the dielectric thin film 5a is deposited in a low-temperature environment (for example, less than 230°C), the initial film forming state of the dielectric thin film 5a will be poor, the compactness of the dielectric thin film 5a will be reduced, the roughness of the dielectric thin film 5a will be high, the refractive index of the dielectric thin film 5a will be small, and it is difficult to meet the design requirements of the optical properties of the metasurface array layer obtained by subsequent etching, which requires a high refractive index.

[0106] The embodiment of the present application can increase the ionization ratio of the silicon-containing gas in the vacuum reaction chamber by limiting the reaction conditions for preparing the dielectric thin film 5a, i.e., the preset pressure, the second radio frequency power, and the reaction gas, so that more silicon elements participate in the reaction process, and the total amount of residual gas in the vacuum reaction chamber can be reduced, so that the plasma energy is more concentrated, which can reduce the generation of defects in the dielectric thin film 5a, so that the dielectric thin film 5a has a better compactness, reduces the roughness of the dielectric thin film 5a, and improves the refractive index of the isolation dielectric thin film 5a. In this way, good deposition of the dielectric thin film 5a in a low-temperature environment (or under the protection of the color filter 31) is also achieved.

[0107] For example, the refractive index of the dielectric thin film 5a is greater than or equal to 1.8. Alternatively, the refractive index of the dielectric thin film 5a can be 1.8, 1.88, 1.9, 2.1, 2.3, 2.5, or 2.6, etc. Here, the refractive index of the dielectric thin film 5a and the refractive index of the isolation dielectric layer 4 have a difference. That is, the refractive index of the dielectric thin film 5a and the refractive index of the isolation dielectric layer 4 are not both 1.8. Further, the greater the difference between the refractive index of the dielectric thin film 5a and the refractive index of the isolation dielectric layer 4, the better the optical performance of the image sensor can be met.

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

[0109] In this way, the dielectric thin film 5a can have a higher compactness and fewer defects, meet the design requirements of the metasurface array layer formed by subsequent etching, and effectively improve the light amount and light utilization rate of the prepared image sensor.

[0110] S400, as shown in FIG. 7f, 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] Exemplarily, the embodiment of the present application can adopt a photolithography process to etch the dielectric film 5a. Specifically, as shown in FIG. 7c, the embodiment of the present application can first form a hard mask layer 6a on the side of the dielectric film 5a away from the circuit layer 1, and form a photoresist layer 7a on the side of the hard mask layer 6a away from the circuit layer 1; as shown in FIG. 7d, then the photoresist layer 7a is exposed and developed to obtain a patterned photoresist layer 7; as shown in FIG. 7e, then the hard mask layer 6a is etched with the patterned photoresist layer 7 as a mask to obtain a patterned hard mask layer 6; as shown in FIG. 7f, the dielectric film 5a is etched based on the patterned hard mask layer 6 to obtain the metasurface array layer 5. As shown in FIG. 8 and FIG. 9, the embodiment of the present application can further remove the patterned photoresist layer 7 and the patterned hard mask layer 6 to obtain the image sensor 120.

[0112] The metasurface array layer 5 described above includes a plurality of nano-pillar structures, and the shape of the plurality of nano-pillar structures in orthographic projection on a reference plane and the size and arrangement of the plurality of nano-pillar structures can be selected as needed, and the embodiment of the present application does not limit the same. The reference plane is perpendicular to the thickness direction of the metasurface array layer 5.

[0113] It can be understood that the metal structure (including but not limited to the metal grid 32, etc.) formed before the dielectric film 5a can cause the problem of excessive trace metal, affect the secondary incoming line, and it is difficult to etch the dielectric film 5a. Therefore, the embodiment of the present application forms the isolation dielectric layer 4 before forming the dielectric film 5a, and covers and shields the metal structure (including but not limited to the metal grid 32, etc.), which can effectively reduce the pollution of trace metal and avoid affecting the secondary incoming line.

[0114] The embodiment of the present application respectively tests the trace metal before and after the formation of the isolation dielectric layer 4, and the results are shown in Table 1 below, wherein the "front side contamination test" refers to the contamination test of the trace metal 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 can be seen from Table 1, before the isolation medium layer 4 is formed, the contamination of various trace metals is basically more than the standard of the subsequent in-line process; and after the isolation medium layer 4 is formed, the contamination of various trace metals is basically reduced to within the standard of the subsequent in-line process. This means that by forming the isolation medium layer 4, the contamination of trace metals can be effectively reduced. In this way, the secondary in-line process can be more smoothly carried out, and the etching of the medium film 5a and the mass production of the image sensor 120 can be realized. Among them, aluminum belongs to the inherent structure on the initial image sensor 120a, and does not affect the subsequent secondary in-line process.

[0117] The super surface array layer 5 formed by etching the medium film 5a has strong dispersion characteristics, has different deflection effects on different colors of light (or different wavelengths of light), and can realize the function of directing and deflecting different colors of light to specific color filters 31. In the process of transmitting different colors of light to specific color filters 31, the light will pass through the isolation medium layer 4. The arrangement of the isolation medium layer 4 can also provide a certain optical path (i.e., provide a certain transmission distance for light), so that different color filters 31 can more accurately receive light of a specific color.

[0118] Taking the multiple color filters 31 including multiple red color filters, multiple green color filters and multiple blue color filters as an example. For example, as shown in (a) and (b) of FIG. 10, the color pixel units in the image sensor are arranged in an RGGB manner. For example, after external light is incident on the super surface array layer 5, the multiple nano columnar structures in the super surface array layer 5 can cooperate with each other to refract the external light, separate red light, green light and blue light, and deflect the red light through the isolation medium layer 4 to the red color filter, deflect the green light through the isolation medium layer 4 to the green color filter, and deflect the blue light through the isolation medium layer 4 to the blue color filter.

[0119] Further, after the light of different colors passes through the corresponding color filter 31, it can be absorbed by the photoelectric conversion element 21 in the photosensitive layer 2 to be converted into an electrical signal.

[0120] In this way, compared with the way of separately arranging the filter array layer 3, the preparation method provided in the embodiments of the present application combines the initial image sensor 120a and the super surface array layer 5 with each other to form a “MetaCIS” structure, and can use the large dispersion effect of the prepared super surface array layer 5 to deflect the light (such as red light and blue light) originally filtered and absorbed by a certain color filter 31 to the color filter 31 of the corresponding color. In this way, the light amount of the prepared image sensor can be improved, the pixel-level spectral light splitting function can be realized, the light utilization rate of the prepared image sensor can be enhanced, and the signal-to-noise ratio and weak light capability of the electronic device to which the image sensor is applied can be improved.

[0121] Thus, the method for manufacturing the image sensor provided by some embodiments of the present application can improve the proportion of ionization of the silicon-containing gas in the vacuum reaction cavity by forming the dielectric film 5a on the initial image sensor 120a including the filter array layer 3 and limiting the formation conditions (such as the preset pressure, the preset radio frequency power, the reaction gas, etc.) of the dielectric film 5a, so that the refractive index of the formed dielectric film 5a is greater than or equal to 1.8, and then etching the dielectric film 5a to form the metasurface array layer 5, thereby not only realizing good deposition of the dielectric film 5a in a low-temperature environment below 230°C, protecting the filter array layer 3, and ensuring good optical properties of the dielectric film 5a, so that the metasurface array layer 5 can have strong dispersion characteristics to meet the design requirements, but also improving the light amount and light utilization of the manufactured image sensor by using the metasurface array layer 5 on the basis of better eliminating optical crosstalk by using the filter array layer 3.

[0122] Moreover, by forming the isolation dielectric layer 4 before forming the dielectric film 5a, not only can the metasurface array layer 5 and the filter array layer 3 be separated to provide a certain optical path for the light scattered by the metasurface array layer 5, but also the isolation dielectric layer 4 can cover the metal structure formed before, reduce metal pollution, facilitate secondary wiring, and etch the metasurface array layer 5.

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

[0124] In this way, not only can the isolation dielectric layer 4 provide sufficient optical path to facilitate the color filters 31 in the filter array layer 3 to accurately receive light of corresponding colors, but also can ensure that the isolation dielectric layer 4 effectively covers the trace metal (or metal structure) below to effectively reduce the pollution of the trace metal.

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

[0126] In this way, the thickness of the metasurface array layer 5 formed by subsequent etching can meet the design requirements, and the metasurface array layer 5 can have strong dispersion characteristics (or large dispersion effect), so as to effectively improve the light quantity and light utilization rate of the image sensor formed.

[0127] In some examples, in the above S200 and S300, the maximum value of the preset temperature range 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 working temperature of the filter array layer 3.

[0129] Since the maximum working temperature of the color filter 31 in the filter array layer 3 may fluctuate up and down, the maximum value of the preset temperature range is set to be different from the maximum working temperature (i.e. 230°C) of the filter array layer 3 in the present embodiment, which can effectively protect the color filter 31 in the filter array layer 3 without causing a large adverse effect on the refractive index of the dielectric film 5a (or the metasurface array layer 5).

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

[0131] Generally, the pressure for depositing inorganic materials is relatively large. By reducing the preset pressure, the maximum value of the preset pressure range is 1000 mTorr in the present embodiment, which can reduce the total amount of residual gas in the vacuum reaction chamber, so that the plasma energy is more concentrated, and the generation of defects in the isolation dielectric layer 4 and the dielectric film 5a is reduced, thereby effectively reducing the roughness of the isolation dielectric layer 4 and the dielectric film 5a.

[0132] Further, the preset pressure range can be, for example, 500 mTorr-1000 mTorr. Alternatively, 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] Therefore, the total amount of residual gas in the vacuum reaction cavity can be effectively reduced, the plasma energy can be more concentrated, and the generation of defects in the isolation medium layer 4 and the medium film 5a can be greatly reduced, and the roughness of the isolation medium layer 4 and the medium film 5a can be greatly reduced.

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

[0135] Table 2

[0136] Specifically, the temperature in the vacuum reaction cavity is maintained at 100°C, the preset pressure is maintained in the range of 500mTorr-1000mTorr, the first preset radio frequency power is high frequency power and is maintained in the range of 20W-100W, the silicon-containing gas with a flow range of 200sccm-500sccm and the laughing gas with a flow range of 400sccm-1000sccm are introduced into the vacuum reaction cavity, and after a deposition time of 15 minutes, a silicon oxide film (i.e., the isolation medium 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, the temperature in the vacuum reaction cavity is maintained at 200°C, the preset pressure is maintained in the range of 500mTorr-1000mTorr, the high frequency power of the second preset radio frequency power is maintained in the range of 20W-70W, the low frequency power of the second preset radio frequency power is maintained in the range of 10W-50W, the silicon-containing gas with a flow range of 200sccm-500sccm and the ammonia gas with a flow range of 400sccm-1000sccm are introduced into the vacuum reaction cavity, and after a deposition time of 45 minutes, a silicon nitride film (i.e., the medium film 5a) is obtained. The silicon-containing gas includes silane and argon, and the volume percentage of silane is 5%.

[0139] It is tested that, as shown in FIG. 11, the refractive index of the isolation medium layer 4 is kept at about 1.47 in the wavelength range of 400 nm-760 nm, satisfying the design requirement of optical characteristics. As shown in FIG. 12, the refractive index of the medium thin film 5a ranges from 1.88 to 1.96 in the wavelength range of 400 nm-760 nm, and the average refractive index is kept at about 1.91; the extinction coefficient of the medium thin film 5a is about less than 0.015. The roughness of the medium thin film 5a is about 4.641 nm. The medium thin film 5a has a higher refractive index, a lower roughness and an extinction coefficient, that is, the medium thin film 5a formed by using the preparation method has a higher compactness, the medium thin film 5a has a very small loss to incident light, and can achieve a very good light splitting function.

[0140] In some embodiments, after the patterned photoresist layer 7 and the patterned hard mask layer 6 are removed, a microlens array layer or the like structure can be further formed on the side of the metasurface array layer 5 away from the circuit layer 1.

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

[0142] In some embodiments, as shown in FIGS. 8 and 9, the image sensor 120 includes an initial image sensor 120a, an isolation medium layer 4 and a metasurface array layer 5. The initial image sensor 120a includes the circuit layer 1, the photosensitive layer 2 and the filter array layer 3 which are arranged in a stack, and the circuit layer 1, the photosensitive layer 2 and the filter array layer 3 can be referred to the related description above, which will not be repeated here.

[0143] Continuing to refer to FIGS. 8 and 9, the isolation medium layer 4 is located on the filter array layer 3. The isolation medium layer 4 has a planar structure and covers the filter array layer 3. Specifically, the isolation medium layer 4 covers the color filters 31 and the metal grating 32 in the filter array layer 3. For example, the refractive index of the isolation medium layer 4 ranges from 1.4 to 1.8. Alternatively, the refractive index of the isolation medium layer 4 can be 1.4, 1.46, 1.48, 1.5, 1.6, 1.7 or 1.8, etc. The smaller the refractive index of the isolation medium layer 4, the better the optical characteristic requirement of the image sensor 120 can be met.

[0144] Continuing to refer to FIGS. 8 and 9, the metasurface array layer 5 is located on the isolation medium layer 4. The metasurface array layer 5 includes, for example, a plurality of nano-columnar structures, and the shape of the projection of the plurality of nano-columnar structures on a reference plane and the size and arrangement of the plurality of nano-columnar structures can be selected according to actual needs, which are not limited in the embodiments of the present application.

[0145] Exemplarily, the refractive index of the metasurface array layer 5 is greater than or equal to 1.8. Alternatively, 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. In this way, the metasurface array layer 5 can meet the design requirements of light splitting, so that the metasurface array layer 5 has the function of light splitting. 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 1.8 at the same time. Further, the greater the difference between the refractive index of the metasurface array layer 5 and the refractive index of the isolation medium layer 4, the better the optical property requirements of the image sensor 120 can be met.

[0146] Further, the above-mentioned metasurface array layer 5 is configured to disperse the light incident to the metasurface array layer 5 and transmit the dispersed light to the filter array layer 3.

[0147] Regarding the transmission process of the light after the light is incident to the metasurface array layer 5, reference can be made to the related description above, which will not be repeated here.

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

[0149] In some embodiments, the thickness of the above-mentioned isolation medium layer 4 ranges from 1 μm to 4 μm. Alternatively, 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] In this way, it can be ensured that the isolation medium layer 4 can provide sufficient optical path, so that each color filter 31 in the filter array layer 3 can accurately receive light of the corresponding color.

[0151] In some embodiments, the thickness of the above-mentioned metasurface array layer 5 ranges from 500 nm to 1000 nm. Alternatively, 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] In this way, the thickness of the metasurface array layer 5 can meet the design requirements, and the metasurface array layer 5 can have strong dispersion characteristics (or large dispersion effect), so as to effectively improve the light quantity and light utilization of the image sensor 120.

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

[0154] In this way, the metasurface array layer 5 can have a high degree of compactness and fewer defects, and can meet the design requirements of light splitting and effectively improve the light quantity and light utilization of the image sensor 120.

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

[0156] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of fabricating an image sensor, characterized by, The preparation method comprises: forming an initial image sensor; the initial image sensor comprises circuit layers, a photosensitive layer and a filter array layer arranged in layers; forming an isolation medium layer on the filter array layer by using a silicon-containing gas and an oxygen-containing gas at a preset temperature range, a preset pressure range and a first preset radio frequency power; the isolation medium layer covers the filter array layer, the refractive index of the isolation medium layer ranges from 1.4 to 1.8, and the maximum value of the preset temperature range is less than 230℃; forming a dielectric film on the isolation medium layer by using the silicon-containing gas and a nitrogen-containing gas at the preset temperature range, the preset pressure range and a second preset radio frequency power; the refractive index of the dielectric film is greater than or equal to 1.8; performing etching on the dielectric film to form a metasurface array layer; the metasurface array layer is configured to disperse light incident to the metasurface array layer and transmit the dispersed light to the filter array layer.

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

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

4. The production method according to claim 3, characterized by, The preset pressure range is 500mTorr-1000mTorr.

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

6. The production method according to any one of claims 1 to 5, characterized by, The second preset radio frequency power comprises 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 production method according to any one of claims 1 to 6, characterized by, In the process of forming the isolation medium layer, the flow rate ratio of the silicon-containing gas to 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 200sccm to 500sccm, and the flow rate of the oxygen-containing gas ranges from 400sccm to 1000sccm.

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

10. The production method according to any one of claims 1 to 8, characterized by, In the process of forming the dielectric film, the flow rate ratio of the silicon-containing gas to the nitrogen-containing gas ranges from 1:5 to 5:

4.

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

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

13. The production method according to any one of claims 1 to 12, characterized by, The silicon-containing gas further comprises silane, and the volume percentage of the silane ranges from 3% to 10%; the oxygen-containing gas comprises laughing gas; and the nitrogen-containing gas comprises ammonia.

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

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

16. An image sensor, comprising: The image sensor is formed by using the preparation method in any one of claims 1-15. The image sensor comprises: An initial image sensor comprising a circuit layer, a photosensitive layer and a filter array layer arranged in a stack; An isolation medium layer located on and covering the filter array layer; the isolation medium layer has a refractive index ranging from 1.4 to 1.8; and A metasurface array layer located on the isolation medium layer; the metasurface array layer has a refractive index 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 of claim 16, wherein, The thickness of the isolation medium layer ranges from 1 μm to 4 μm, and the thickness of the metasurface array layer ranges from 500 nm to 1000 nm.

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

19. A camera module, comprising: The camera module comprises: The image sensor according to any one of claims 16-18; and A lens assembly located on the light entrance side of the image sensor.

20. An electronic device, comprising: The electronic device comprises: The camera module according to claim 19; and A processor electrically connected to the image sensor in the camera module.

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