Novel metamaterial multispectral imaging chip and preparation method thereof

Abstract

The present invention discloses a novel metamaterial multispectral imaging chip and a preparation method thereof, belonging to the technical field of optical sensors, comprising: a multi-channel metamaterial filter array, a microlens array and an image sensor, wherein the multi-channel metamaterial filter array is located between the microlens array and the image sensor and integrated with the image sensor; the multi-channel metamaterial filter array includes a base layer, a nanopore array structure layer and a plasma resonance effect covering layer, the plasma resonance effect covering layer is located on the upper surface of the nanopore array structure layer, and the base layer is located on the lower surface of the nanopore array structure layer. The present invention directly constructs and packages the multi-channel metamaterial filter array and the microlens array on a commercial CMOS image sensor silicon chip, realizes imaging and spectral acquisition of multiple wavelength channels, and the constructed multispectral imaging chip is compact.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optical sensors, and particularly relates to a novel metamaterial multispectral imaging chip and a preparation method thereof. Background Art

[0002] Optical sensor devices are becoming increasingly popular in the fields of automotive, industrial, medical, and consumer electronics. In particular, in recent years, the development of smartphones, intelligent lighting, digital electronic products, intelligent manufacturing, and Internet of Things technologies has promoted the continuous development of optical sensor device technology towards the direction of intelligence, miniaturization, and integration. As an important application category of optical sensors, spectrometers (spectral sensors) are also gradually emerging. Traditional multispectrometers have been applied in the fields of unmanned aerial vehicle detection (ground target detection and monitoring, environment, crop monitoring, etc.), fire protection and security, medical and health (fundus diseases, blood vessels, teeth, and cancer detection, etc.), and forensic identification (fingerprint, blood stain, physical evidence detection, etc.). However, the vast majority of traditional spectrometers are complex, costly, bulky, consume a large amount of power, and high-precision measurements can only be carried out within a few tens of centimeters.

[0003] With the rapid growth of market demand, the size of spectrometers has hindered their popularization in a wider range of fields. Therefore, there is an urgent need in the market for high-performance compact spectrometers, and continuously reducing the size of spectral sensors has become a current research hotspot. To miniaturize spectrometers, relevant researchers have made various attempts, such as traditional dispersion methods, Fourier transform interference technology (Fourier Transform Infrared, FTI), and using detectors with random filter arrays and narrowband filters.

[0004] Compared with dispersion and Fourier transform interference systems, the integration of filter arrays and detectors has the advantage of not requiring a long optical path and precise alignment of optical components to obtain high resolution. In addition, integrating filter arrays with detectors such as charge-coupled devices (Charge Coupled Device, CCD) or CMOS image sensors (CMOS Imagr Sensor, CIS) can achieve hyperspectral imaging by capturing a two-dimensional image in a single shot. In particular, compared with the random filter scheme, the integration of narrowband filter arrays does not require post-processing analysis. However, to obtain high resolution, a large number of channels are required, which means a more complex manufacturing process, such as etching and deposition, because each channel requires a different thickness of the thin film.

[0005] The industry has studied the resonant structures of narrow - bandpass filters used in spectrometers, but most studies have been limited to changing the thickness of dielectric multilayers to form optical cavities with different wavelengths and quality factors. This is troublesome for large - scale production of devices because it requires excessive dielectric deposition, etching, and lithography steps, especially in manufacturing processes at the pixel - size level.

[0006] In the related art, a multi - spectral chip based on metasurface narrow - band filtering generally includes a planar array image sensor and a metasurface - structured filter array. The metasurface - structured filter array includes two layers of nano - film passivation layers and a periodic array structure of metal nano - holes located between the two layers of nano - film passivation layers; the metasurface - structured filter array is located on the planar array image sensor; the periodic array structure of metal nano - holes includes a metal - dielectric film layer, and the metal - dielectric film layer has a periodic nano - hole array with different sizes. By fabricating periodic nanostructure arrays with different sizes on a metal - dielectric film layer of the same thickness, narrow - band filtering of the target image in the multi - spectral band is achieved; it is suitable for more refined spectral information acquisition, and by fabricating metal nano - periodic structures on the surface of the image sensor, a planar array multi - spectral chip is realized, which is easier to implement in terms of technology and has wide applicability.

[0007] However, this multi - spectral chip based on metasurface narrow - band filtering is only a multi - spectral chip that can only measure spectra but cannot achieve multi - spectral imaging. Summary of the Invention

[0008] The technical problem to be solved by the present invention is how to achieve spectral imaging and spectral acquisition of multiple wavelength channels.

[0009] The present invention solves the above - mentioned technical problem by the following technical means:

[0010] On the one hand, the present invention proposes a multi - spectral imaging chip, which includes: a multi - channel metamaterial filter array, a microlens array, and an image sensor. The multi - channel metamaterial filter array is located between the microlens array and the image sensor and is integrated with the image sensor;

[0011] The multi - channel metamaterial filter array includes a base layer, a nano - hole array structure layer, and a plasma resonance effect covering layer. The plasma resonance effect covering layer is located on the upper surface of the nano - hole array structure layer, and the base layer is located on the lower surface of the nano - hole array structure layer.

[0012] The present invention uses the sub-wavelength nanostructures of the metasurface to form a multi-channel metamaterial filter array. Utilizing the plasmon resonance and extraordinary optical transmission effects, the transmittance and bandwidth of the spectrum are modulated by changing the aperture diameter and arrangement period of the nano-holes to achieve light output in different bands. The above multi-channel metamaterial filter array and microlens array are directly constructed and packaged on a commercial CMOS image sensor silicon chip. The combination of the microlens array and the multi-channel metamaterial filter array forms sub-images in different bands, enabling multiple sub-images in different bands to be simultaneously formed on the CMOS image sensor. Using this multi-spectral imaging chip, the multi-channel images can be integrated, compared, analyzed, and processed to obtain multi-spectral images and spectral information of the imaged object, realizing imaging and spectral acquisition in multiple wavelength channels. Moreover, the constructed multi-spectral imaging chip is compact, with narrowband high efficiency, low crosstalk with adjacent channels, and multi-spectral resolution.

[0013] Further, the base layer is prepared from a polymer material, the plasmon resonance effect covering layer is prepared from a composite material of metal and semiconductor oxide, and the nano-hole array structure layer is prepared from a photo-curing material.

[0014] Further, the nano-hole array structure layer uses a 3×3 color filter.

[0015] In addition, the present invention also proposes a multi-spectral imaging system, which includes a plurality of the above-mentioned multi-spectral imaging chips. The plurality of multi-spectral imaging chips are packaged using a grid array with an integrated aperture; the output of the multi-spectral imaging chip is connected to a host microprocessor.

[0016] Further, each multi-spectral imaging chip is connected to a drive controller.

[0017] In addition, the present invention also proposes a preparation method for a multi-spectral imaging chip, which includes:

[0018] Performing photolithography and etching processes on a solid wafer to obtain a three-dimensional nano-structure array on the wafer surface;

[0019] Performing nano-scale imprinting processes on the solid wafer to transfer the three-dimensional nano-structure array to the surface of the polymer material of the flexible substrate, obtaining a three-dimensional nano-structure polymer film;

[0020] Performing alternating deposition of multiple layers of metal and metal oxide on the surface of the three-dimensional nano-structure polymer film to form a multi-channel metamaterial filter array film;

[0021] Combining, packaging, and testing the multi-channel metamaterial filter array film, microlens array film, and CMOS image sensor chip to prepare a multi-spectral imaging chip.

[0022] Furthermore, the multi-channel metamaterial filter array film, the microlens array film and the CMOS image sensor chip are packaged and tested to prepare a multispectral imaging chip, including:

[0023] Performing system packaging on the multi-channel metamaterial filter array film and the CMOS image sensor chip;

[0024] The microlens array film is integrated on the multi-channel metamaterial filter array film and connected and packaged with the lens group of the CMOS image sensor chip.

[0025] Furthermore, the three-dimensional nanostructure is a nanocolumn or a nanopore.

[0026] Furthermore, the solid wafer is a solid semiconductor or semiconductor oxide;

[0027] The CMOS image sensor chip is matched with a supporting circuit.

[0028] The advantages of the present invention are:

[0029] (1) The present invention uses the sub-wavelength nanostructure of the metasurface to form a multi-channel metamaterial filter array, utilizes plasma resonance and unconventional optical transmission effects, and modulates the transmittance and bandwidth of the spectrum by changing the aperture and arrangement period of the nanopores to achieve light output in different bands. The multi-channel metamaterial filter array and microlens array are directly constructed and packaged on a commercial CMOS image sensor silicon chip. The combination of the microlens array and the multi-channel metamaterial filter array forms sub-images of different bands, so that multiple sub-images of different bands can be formed on the CMOS image sensor at the same time. The multi-spectral imaging chip can be used to integrate, compare and analyze the multi-channel images to obtain multi-spectral images and spectral information of the imaged object, thereby realizing imaging and spectral acquisition of multiple wavelength channels. The constructed multi-spectral imaging chip is compact, has narrow-band high efficiency, low crosstalk with adjacent channels, and multi-spectral resolution.

[0030] (2) Based on the physical properties of the interaction between light and micro-nano structures and materials, a combination of different micro-nano optical structures is used to achieve the filtering effect that can be achieved by traditional filter films.

[0031] (3) Since narrow-bandpass filtering is tuned by a subwavelength grating structure rather than by changing the layer thickness, all filter channels can be manufactured on a large-area wafer through a one-step photolithography process. This scheme simplifies manufacturing, significantly reduces costs, and is fully compatible with CMOS processes.

[0032] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. Brief Description of the Drawings

[0033] Figure 1 is a schematic structural diagram of an image sensor in an embodiment of the present invention;

[0034] Figure 2 is a schematic structural diagram of a multi-channel metamaterial filter array in an embodiment of the present invention;

[0035] Figure 3 is an optical image (pixel size 2.2 microns) of a filter array inlaid with nine-segment wave □ pixels in an embodiment of the present invention, where the left side is an enlarged view of the color filter pixel array and the right side is a reduced view;

[0036] Figure 4 is a schematic flowchart of a preparation method of a multi-spectral imaging chip in an embodiment of the present invention.

[0037] In the figure:

[0038] 10 - lens group; 21 - base layer; 22 - nanohole array structure layer; 23 - plasma resonance effect covering layer. Detailed Embodiments

[0039] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0040] As Figures 1 to 2 shown, a multi-spectral imaging chip is proposed in the first embodiment of the present invention. The chip includes: a multi-channel metamaterial filter array, a microlens array and an image sensor. The image sensor is as Figure 1 shown. The multi-channel metamaterial filter array is located between the microlens array and the image sensor and integrated with the image sensor. The microlens array and the multi-channel metamaterial filter array are connected above the lens group 10 of the image sensor;

[0041] The multi-channel metamaterial filter array includes a base layer 21, a nanohole array structure layer 22 and a plasma resonance effect covering layer 23. The plasma resonance effect covering layer 23 is located on the upper surface of the nanohole array structure layer 22, and the base layer 21 is located on the lower surface of the nanohole array structure layer 22.

[0042] It should be noted that in this embodiment, a metasurface material is used to fabricate a multi-channel metamaterial filter array. The metasurface material refers to an artificial layered material with a thickness less than the wavelength, which can flexibly and effectively control characteristics such as the polarization, amplitude, phase, polarization mode, and propagation mode of electromagnetic waves. Different metasurface filter structures will filter light of different wavelengths.

[0043] In this embodiment, the multi-channel metamaterial filter array and the micro-lens array are connected and integrated on the top of the lens group 10 of the CMOS image sensor. The obtained multi-spectral imaging chip is a compact multi-spectral sensor chip, which has narrow-band high efficiency, low crosstalk with adjacent channels, and multi-spectral resolution. The combination of the micro-lens array and the multi-channel metamaterial filter array forms sub-images of different bands, enabling multiple sub-images of different bands to be formed simultaneously on the CMOS image sensor. By using this multi-spectral imaging chip, multi-channel images can be integrated, compared, and analyzed to obtain multi-spectral images and spectral information of the imaged object, realizing imaging and spectral acquisition in multiple wavelength channels.

[0044] In one embodiment, the base layer 21 is prepared from a polymer material, the plasmon resonance effect covering layer 23 is prepared from a composite material of metal and semiconductor oxide, and the nano-pore array structure layer 22 is prepared from a photo-curing material.

[0045] It should be noted that the base layer 21 is used as a support and protection layer for the filter structure. The nano-pore array structure layer 22 includes multiple filter regions, each filter region corresponding to multiple pixels of the image sensor. Each filter region includes a metal nano-pore array with the same aperture and period. The apertures and periods of the metal nano-pore arrays in different filter regions are different. The plasmon resonance effect covering layer 23 is used to utilize the plasmon resonance and extraordinary optical transmission effect to modulate the transmittance and bandwidth of the spectrum by changing the aperture and arrangement period of the nano-pores, realizing the output of light in different bands.

[0046] Furthermore, the meta-material multi-spectral sensor technology (MMM sensor) is based on the physical characteristics of the interaction between light and micro-nano structures and materials. By using the combination of different micro-nano optical structures, the filter effect achievable by traditional filter films can be achieved. The existing filter structures currently include multi-layer interference films, structures based on guided-mode resonance, one-dimensional gratings, metal nano-pores, etc. In this embodiment, the metal nano-pore structure is used as the preferred metasurface structure. By utilizing the surface plasmon resonance effect, the transmittance and bandwidth of the spectrum are modulated by changing the aperture and arrangement period of the nano-pores, realizing the output of light in different bands. And in terms of process, nano-pore arrays with different parameters can be fabricated only through one photolithography process, greatly simplifying the process difficulty and complexity.

[0047] In one embodiment, the nano-pore array structure layer 22 employs a 3×3 color filter.

[0048] In this embodiment, a prototype test is conducted on the multi-spectral imaging chip. During the test, a "super pixel" is fabricated using micro-nano optical structures with different diameters, and a 3×3 color filter replaces the traditional 2×2 RGB color filter.

[0049] The test results demonstrate that nine different diameters of micro-nano optical structures can accurately select colors. Figure 3 On the left is an enlarged view of the MMMSense color filter pixel array. Each group consists of nine colors and can capture light information in nine different wavelength bands.

[0050] The final prototype test results verify that by fabricating these nine different micro-nano optical structures on a traditional CMOS image sensor, a very small, low-power, and compact multi-spectral imaging sensor can be constructed.

[0051] In addition, a second embodiment of the present invention further proposes a multi-spectral imaging system. The system includes a plurality of the multi-spectral imaging chips proposed in the first embodiment above, and a grid array with an integrated aperture is used for packaging between the plurality of multi-spectral imaging chips; the output of the multi-spectral imaging chip is connected to a host microprocessor.

[0052] Specifically, the MMMSense multi-spectral sensing chip group in this embodiment will consist of three or more highly integrated 6-channel multi-spectral imaging chips. The size of each chip is only about 5×5×3 mm, and it is packaged using a compact grid array with an integrated aperture. Moreover, the master-slave architecture serves as a single logical device, simplifying the system integration process.

[0053] In a multi-light imaging system composed of three 6-channel multi-spectral imaging chips, 18 channels span wavelengths from 410 to 940 nanometers. The chip group applies a master / slave / slave distributed design and each is equipped with 6 spectral sensing channels. The integrated intelligence helps to calibrate the digital output and is managed via the host microprocessor through an optional I2C or UART interface.

[0054] Specifically, the 18 channels of this chip group have wavelength centers at 410, 435, 460, 485, 510, 535, 560, 585, 610, 645, 680, 705, 730, 760, 810, 860, 900, and 940 nm.

[0055] In one embodiment, each multi-spectral imaging chip is connected to a drive controller.

[0056] It should be noted that as a three-chipset, the new device will also include an electronic shutter function with three independent 100mA LED drive controllers, enabling device designers to precisely control multiple light sources and improve spectral sensing performance without additional components.

[0057] In addition, as Figure 4 shown, the third embodiment of the present invention also proposes a method for fabricating a multispectral imaging chip, the method comprising the following steps:

[0058] S10. Perform lithography and etching processes on a solid wafer to obtain a three-dimensional nanostructure array on the wafer surface.

[0059] It should be noted that the solid wafer used in this embodiment is a solid semiconductor or semiconductor oxide wafer widely used in current mainstream wafer fabs.

[0060] Furthermore, the three-dimensional nanostructure is a nanocolumn or nanopore.

[0061] S20. Perform nanoimprinting processes on the solid wafer to transfer the three-dimensional nanostructure array to the surface of a polymer material of a flexible substrate, obtaining a three-dimensional nanostructure polymer film.

[0062] In this embodiment, when preparing the three-dimensional nanostructure polymer film, filter arrays with different wavelengths and densities are designed according to different application scenarios; a suitable micro-nano optical structure substrate material is selected on the surface of a silicon or silicon oxide wafer according to physical principles, and the design is transformed into a micro-nano optical structure or metasurface structure wafer-level lithography mask with corresponding geometric parameters, and the pattern is transferred to the wafer surface.

[0063] S30. Alternately deposit multiple layers of metals and metal oxides on the surface of the three-dimensional nanostructure polymer film to form a multi-channel metamaterial filter array film.

[0064] It should be noted that in this embodiment, reactive ion etching technology and MEMS etching technology are used to etch precise optical micro-nano optical structures on the wafer, ensuring that the etched micro-nano optical structures conform to the designed geometric morphology (shape, height, width, density, etc.). Subsequently, a nano-scale metamaterial layer is deposited to endow it with band-pass filtering properties.

[0065] S40. Combine and package-test the multi-channel metamaterial filter array film, the microlens array film, and the CMOS image sensor chip to fabricate a multispectral imaging chip.

[0066] It should be noted that the MMMSense sensor is based on integrated micro-nano optical system technology on silicon and silicon oxide wafers, utilizing proven NEMS components to create a monolithic integrated optical system. Using reactive ion etching technology, rigorously designed optical NEMS structures can be designed and manufactured on wafers. These structures are then wafer-level packaged and cut into single-chip filter arrays.

[0067] Furthermore, this embodiment requires testing various performance parameters of the multispectral sensor chip units on the wafer, and combining the channel metamaterial filter array film, microlens array film and CMOS image sensor chip that have passed the test into a SIP package, and then encapsulating them with a transparent flattening protective layer (such as glass), performing wafer-level packaging and cutting them into individual multispectral imaging chips.

[0068] In this embodiment, a conventional commercial CMOS image sensor chip wafer with matching supporting circuitry is selected, and the prepared multi-channel metamaterial filter array film, microlens array film, and CMOS image sensor chip are assembled and packaged and tested to manufacture a multispectral imaging chip. Because narrow-bandpass filtering is tuned via a subwavelength grating structure rather than by varying layer thickness, all filter channels can be fabricated on a large-area wafer using a single-step photolithography process. This solution simplifies manufacturing, significantly reduces costs, and is fully compatible with CMOS processes. The device is used to integrate, compare, and analyze multi-channel images to obtain multispectral images and spectral information of the imaged object, thereby achieving spectral imaging and spectral acquisition of multiple wavelength channels.

[0069] Moreover, the production and processing characteristics of semiconductor wafers greatly improve production capacity and reduce costs; and integrating all optical components on a single chip can make the optical system more reliable, better avoid the negative effects of shock or vibration, and have high reliability.

[0070] Furthermore, since the multispectral imaging chip prepared in this embodiment can be manufactured below 150°C, it can be integrated into other ICs, such as photodetectors, in a monolithic form, thereby realizing a very compact and cost-effective hyperspectral imaging solution that can meet the requirements of consumer applications.

[0071] In one embodiment, step S40 includes:

[0072] S41 , performing system packaging on the multi-channel metamaterial filter array film and the CMOS image sensor chip.

[0073] S42, integrating the microlens array film on the multi-channel metamaterial filter array film and connecting and packaging it with the lens group of the CMOS image sensor chip.

[0074] It should be noted that the sensor chips prepared by this method can be used to develop a rich product line of embedded multi-spectral image sensors suitable for different application scenarios, create and sell sensors and modules, hardware systems and databases, service platforms (hardware, databases and artificial intelligence, data mining and decision-making), integrate with various technical nodes of the Internet of Things, and be applied to multiple related industries such as big health, smart cities, environmental monitoring, security, automotive sensing, and remote sensing.

[0075] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0076] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0077] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A multispectral imaging chip, characterized in that, The chip comprises: a multi-channel metamaterial filter array, a microlens array and an image sensor, wherein the multi-channel metamaterial filter array is located between the microlens array and the image sensor and is integrated with the image sensor; The multi-channel metamaterial filter array includes a base layer, a nanohole array structure layer and a plasma resonance effect covering layer, wherein the plasma resonance effect covering layer is located on the upper surface of the nanohole array structure layer, and the base layer is located on the lower surface of the nanohole array structure layer; The nanohole array structure layer includes multiple filtering areas, each filtering area corresponds to multiple pixels of the image sensor, each filtering area includes a metal nanohole array with the same aperture and period, and the apertures and periods of the metal nanohole arrays in different filtering areas are different.

2. The multispectral imaging chip according to claim 1, wherein The base layer is made of polymer material, the plasma resonance effect covering layer is made of metal and semiconductor oxide composite material, and the nanopore array structure layer is made of photocurable material.

3. The multispectral imaging chip according to claim 1, characterized in that, The nanopore array structure layer adopts a 3×3 color filter.

4. A multispectral imaging system, characterized in that, The system comprises a plurality of multispectral imaging chips as claimed in claim 1 or 2, wherein the plurality of multispectral imaging chips are packaged in a grid array with an integrated aperture; and the output of the multispectral imaging chip is connected to a host microprocessor.

5. The multispectral imaging system according to claim 4, characterized in that, Each of the multispectral imaging chips is connected to a driving controller.

6. A method for preparing a multi-spectral imaging chip according to any one of claims 1-3, characterized in that, The method comprises: Perform photolithography and etching processes on a solid wafer to obtain a three-dimensional nanostructure array on the wafer surface; Performing nanoscale imprinting processing on the solid wafer to transfer the three-dimensional nanostructure array to the surface of a polymer material on a flexible substrate to obtain a three-dimensional nanostructure polymer film; Alternating deposition of multiple layers of metal and metal oxide on the surface of the three-dimensional nanostructured polymer film to form a multi-channel metamaterial filter array film; The multi-channel metamaterial filter array film, the microlens array film and the CMOS image sensor chip are assembled and packaged for testing to prepare a multispectral imaging chip.

7. The preparation method of the multispectral imaging chip according to claim 6, wherein, The multi-channel metamaterial filter array film, the microlens array film and the CMOS image sensor chip are combined, packaged and tested to prepare a multispectral imaging chip, including: Performing system packaging on the multi-channel metamaterial filter array film and the CMOS image sensor chip; The microlens array film is integrated on the multi-channel metamaterial filter array film and connected and packaged with the lens group of the CMOS image sensor chip.

8. The method for preparing a multi-spectral imaging chip according to claim 6, wherein The three-dimensional nanostructure is a nanocolumn or a nanopore.

9. The method for preparing a multi-spectral imaging chip according to claim 6, wherein, The solid wafer is a solid semiconductor or a semiconductor oxide; The CMOS image sensor chip is matched with a supporting circuit.

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