A metal-dielectric hybrid material FP cavity filter array and its preparation method

Abstract

The present invention relates to a metal-dielectric hybrid material FP cavity filter array structure and a preparation method thereof. The array structure includes an SiO2 substrate, a bottom high-reflection film, a spacer layer, and a top high-reflection film from bottom to top. Among them, the high-reflection film is a multi-layer film of a metal-dielectric hybrid material with an Ag / SiO2 / TiO2 film system; the spacer layer is a photoresist spacer layer with different heights prepared by electron beam direct writing grayscale lithography technology, which is used to correspond to spectra of different wavelengths. Compared with the prior art, the present invention uses electron beam direct writing grayscale lithography technology to prepare photoresist spacer layers with different heights, which has high direct writing efficiency, and uses a multi-layer film of a metal-dielectric hybrid material to replace the traditional metal reflection layer, greatly improving the spectral performance of the FP cavity filter array.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral imaging, and particularly relates to a metal-dielectric hybrid material FP cavity filter array and a preparation method thereof. Background Art

[0002] Spectral imaging technology, especially hyperspectral and ultraspectral imaging, has very wide applications in environmental monitoring, biomedicine, space remote sensing and even military reconnaissance. A variety of application scenarios have put forward extremely high technical requirements for the sensitivity and resolution of spectrometers.

[0003] Since the spectral resolution is inversely proportional to the optical path length, traditional spectrometers based on diffraction gratings are bulky and cannot be made handheld, portable and miniaturized.

[0004] The FP (Fabry-Perot) resonant cavity filter structure with broadband high reflectors combined with an image sensor, although solves the problem of low integration degree, but for the existing such FP cavity band-pass filter arrays, the number of channels is proportional to the length of the spacer layer, that is, the number of spacer layers with different heights, and the spectral resolution is proportional to the reflectivity of the upper and lower high-reflection films. The preparation process is complex by means of combined deposition / etching technology, and the preparation cost is high.

[0005] In addition, the FP cavity band-pass filter arrays prepared by lithography technology usually use metal materials as the upper and lower high-reflection films. Due to the absorption characteristics of metals in the infrared and visible light bands, it is difficult to improve the spectral resolution of such FP filter arrays. At the same time, due to the narrow reflection bandwidth of pure dielectric materials, it is difficult to provide more spectral channels in a broadband range. Therefore, there is currently no good way to balance the spectral resolution and the coverage bandwidth at the same time.

[0006] Aiming at the above problems, it is urgent to design a new type of FP cavity filter array and a preparation method thereof, which can prepare in large area, in large quantities and with high repetition rate while improving the spectral performance of the FP cavity filter structure, so as to promote the practical application of spectrometers. Summary of the Invention

[0007] The purpose of the present invention is to provide a metal-dielectric hybrid material FP cavity filter array and a preparation method thereof with high spectral performance, large coverage bandwidth and simple preparation method, in order to overcome the defects of the existing technologies described above.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] According to the first aspect of the present invention, a metal-dielectric hybrid material FP cavity filter array structure is provided. The array structure includes a SiO2 substrate, a bottom high-reflection film, a spacer layer and a top high-reflection film from bottom to top;

[0010] Among them, the high-reflection film is a metal-dielectric hybrid material multi-layer film of an Ag / SiO2 / TiO2 film system; the spacer layer 3 is a photoresist spacer layer with different thicknesses prepared by electron beam direct writing grayscale lithography technology, which is used to correspond to spectra of different wavelengths.

[0011] Preferably, the thickness λ of the photoresist spacer layer is:

[0012]

[0013] In the formula, d is the height of the square array, n is the refractive index, and nd is the optical thickness of the spacer layer; and are the reflection phases of the bottom high-reflection film and the top high-reflection film respectively; k is the set interference order.

[0014] According to the second aspect of the present invention, a preparation method for the metal-dielectric hybrid material FP cavity filter array structure is provided, and the method includes the following steps:

[0015] Step S1: Prepare a metal-dielectric hybrid material multi-layer film of an Ag / SiO2 / TiO2 film system on a SiO2 substrate by ion beam sputtering deposition technology to obtain a bottom high-reflection film;

[0016] Step S2: Spin-coat a layer of photoresist with a set thickness on the surface of the bottom high-reflection film obtained in step S1 by a spin coater, and then spin-coat a layer of conductive adhesive with a set thickness;

[0017] Step S3: Expose the photoresist in step S2 by electron beam direct writing grayscale lithography technology, and different-height photoresist spacer layers are obtained after development; among them, the exposure area corresponds one-to-one with the shape of the sensor pixel;

[0018] Step S4: On the different-height photoresist spacer layers prepared in step S3, prepare a top high-reflection film by the method of step S1 using ion beam sputtering deposition technology to obtain a metal-dielectric hybrid material FP cavity filter array structure.

[0019] Preferably, step S1 is specifically: preparing a bottom Ag film on a SiO2 substrate by thermal evaporation, then depositing SiO2 by electron beam evaporation, and finally preparing TiO2 film by atomic layer deposition.

[0020] Preferably, the photoresist in step S2 is PMMA photoresist.

[0021] Preferably, the thickness of the photoresist in step S2 is controlled by the rotation speed of the spin coater.

[0022] Preferably, the spin coating parameters of the photoresist in step S2 are set as follows: rotation speed 2000 - 3000 r / min; thickness 500 - 650 nm; baking is performed using a hot plate at a temperature of 178 - 182 °C for 8 - 12 minutes to cure it.

[0023] Preferably, the spin coating parameters of the conductive adhesive in step S2 are set as follows: rotation speed 4000 - 5000 r / min, thickness 30 - 50 nm; baking is performed using a hot plate at a temperature of 87 - 93 °C for 1.8 - 2.2 minutes.

[0024] Preferably, in step S3, electron beam direct writing grayscale lithography technology is used to expose the photoresist in step S2, and after development, a photoresist spacer layer with different heights is obtained. Specifically:

[0025] Exposure parameters are set as follows: beam spot current 9.8 - 10.2 nA, beam spot size 15 - 25 nm, exposure dose 150 μC / cm2 - 250 μC / cm2; the thickness of the photoresist spacer layer is controlled by the exposure dose and development parameters;

[0026] Development parameters are set as follows: after exposure, first rinse off the conductive adhesive with deionized water for 0.5 - 1 minute; then perform development. The developer is a mixed solution of isopropyl alcohol and deionized water with a mixing ratio of 1:1, development temperature 22.8 °C - 23.2 °C, development time 4 - 5 minutes; rinse in deionized water for 0.5 - 1 minute.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1) High efficiency of electron beam grayscale direct writing: The adopted electron beam direct writing grayscale lithography process can, by strictly controlling the exposure dose and optimizing the development parameters, obtain the designed multi-channel FP cavity filter array in one go after development. Regardless of the number of channels, only single exposure is required. Therefore, compared with the traditional methods of combined deposition, combined etching, and alignment, the present invention can achieve the preparation of a large number of FP cavity filter array structures with high repeatability, greatly reducing the preparation difficulty of this type of spectral device, reducing the preparation cost, and also improving the yield of preparation;

[0029] 2) Greatly improve the spectral performance of the FP cavity filter array: Aiming at the defect that traditional FP filter arrays mostly use metal as the reflective layer and have large spectral losses, the present invention uses a metal-dielectric hybrid material multi-layer film to replace the traditional metal reflective layer, reducing spectral absorption, increasing the reflectivity and spectral resolution, and effectively improving the spectral performance of the filtering device;

[0030] 3) Spin a layer of conductive adhesive after spin coating the photoresist, weakening the charge accumulation effect in electron beam exposure. Description of the Drawings

[0031] Figure 1 Schematic structural diagram of the metal-dielectric hybrid material FP cavity filter array of the present invention;

[0032] Figure 2 Detailed structural diagram of the metal-dielectric hybrid material FP cavity filter array of the present invention;

[0033] Figure 3 Spectral curves of the FP cavity filter structure at different wavelengths;

[0034] Reference numerals: 1 - SiO2 substrate, 2 - bottom high-reflection film, 3 - spacer layer, 4 - top high-reflection film. Detailed implementation manners

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in 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 creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment

[0037] According to the FP cavity filtering principle, a filter array structure with a transmittance greater than 75% and a spectral resolution less than 10 nm in the wavelength range of 400 - 700 nm is designed. As Figure 1 and Figure 2 shown, this embodiment provides a metal-dielectric hybrid material FP cavity filter array based on electron beam direct writing gray-scale lithography. The array structure includes a SiO2 substrate 1, a bottom high-reflection film 2, a spacer layer 3, and a top high-reflection film 4 from bottom to top;

[0038] The high-reflection film is a metal-dielectric hybrid material multi-layer film of an Ag / SiO2 / TiO2 film system, and the central wavelength (the position of the wavelength of the transmission response curve of the narrow-band filter) is 550 nm;

[0039] The spacer layer 3 is a photoresist spacer layer with different heights prepared by electron beam direct writing gray-scale lithography technology to correspond to spectra of different wavelengths. The spacer layer is a three-dimensional structure with a size of 5 μm * 5 μm, and the thickness λ is:

[0040]

[0041] In the formula, d is the height of the square array, n is the refractive index, and nd is the optical thickness of the spacer layer; and are the reflection phases of the bottom high-reflection film and the top high-reflection film respectively; k is the set interference order.

[0042] Next, a method embodiment of the present invention is given. A preparation method for the metal-dielectric hybrid material FP cavity filter array structure described above includes the following steps:

[0043] Step S1: Prepare a metal-dielectric hybrid material multi-layer film of an Ag / SiO2 / TiO2 film system on the SiO2 substrate 1 by using an ion beam sputtering deposition technique to obtain a bottom high-reflection film 2. Specifically:

[0044] Prepare a bottom Ag film on the SiO2 substrate by using thermal evaporation, then deposit SiO2 by using electron beam evaporation, and finally prepare a TiO2 film by using atomic layer deposition;

[0045] Process parameter settings for thermal evaporation: The vacuum degree is 1×10 -4 ~1.2×10 -4 Pa, and the Ag deposition rate is

[0046] Process parameter settings for electron beam evaporation deposition: The vacuum degree is 1×10 -4 ~1.2×10 -4 Pa, and the SiO2 deposition rate is

[0047] Process parameter settings for atomic layer deposition: The temperature is 200 °C, the gas flow rate is 90 sccm, and the deposition rate is 0.04 - 0.05 nm / cycle.

[0048] Step S2: Spin-coat a photoresist with a set thickness on the surface of the bottom high-reflection film obtained in step S1 by using a spin coater, and then spin-coat a conductive adhesive with a set thickness; the photoresist in this embodiment is a PMMA photoresist; the thickness of the photoresist is controlled by the rotation speed of the spin coater;

[0049] Spin-coating parameter settings for the photoresist: The rotation speed is 2000 - 3000 r / min; the thickness is 500 - 650 nm; baking is performed using a hot plate at a temperature of 178 - 182 °C for 8 - 12 minutes to cure it;

[0050] Spin-coating parameter settings for the conductive adhesive: The rotation speed is 4000 - 5000 r / min, the thickness is 30 - 50 nm; baking is performed using a hot plate at a temperature of 87 - 93 °C for 1.8 - 2.2 minutes.

[0051] Step S3: Expose the photoresist in step S2 by using an electron beam direct writing grayscale lithography technique, and after development, obtain photoresist spacer layers with different heights. The exposed areas correspond one-to-one to the pixel shapes of the sensor (the sensor in this embodiment is a CCD charge-coupled device or a CMOS complementary metal oxide semiconductor). Specifically:

[0052] Exposure parameter settings: the spot current is 9.8 - 10.2 nA, the spot size is 15 - 25 nm, and the exposure dose is 150 μC / cm2 - 250 μC / cm2; the height of the photoresist spacer layer is controlled by the exposure dose and development parameters;

[0053] Development parameter settings: after exposure, first rinse off the conductive adhesive with deionized water for 0.5 - 1 minute; then perform development. The developer is a mixed solution of isopropyl alcohol IPA and deionized water with a mixing ratio of 1:1, the development temperature is 22.8°C - 23.2°C, and the development time is 4 - 5 minutes; rinse in deionized water for 0.5 - 1 minute;

[0054] Step S4. On the photoresist spacer layers with different heights prepared in step S3, use the ion beam sputtering deposition technique to prepare the top high - reflection film according to the method of step S1, and obtain the metal - dielectric hybrid material FP cavity filter array structure.

[0055] Figure 3 is the spectral curve of the FP cavity filter structure at different wavelengths. It can be seen from the figure that the present invention uses a metal - dielectric hybrid material multi - layer film to replace the traditional metal reflective layer, reducing the spectral absorption, improving the reflectivity and spectral resolution, and effectively improving the spectral performance of the filter device.

[0056] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A preparation method for a metal-dielectric hybrid material FP cavity filter array structure, characterized in that, The array structure includes a SiO2 substrate (1), a bottom high-reflection film (2), a spacer layer (3), and a top high-reflection film (4) from bottom to top; Among them, the high-reflection film is a multi-layer film of a metal-dielectric hybrid material with an Ag / SiO2 / TiO2 film system; the spacer layer (3) is a photoresist spacer layer with different thicknesses prepared by electron beam direct writing gray-scale lithography technology to correspond to spectra of different wavelengths; The method includes the following steps: Step S1: Prepare a multi-layer film of a metal-dielectric hybrid material with an Ag / SiO2 / TiO2 film system on the SiO2 substrate by ion beam sputtering deposition technology to obtain a bottom high-reflection film. Specifically: prepare a bottom Ag film on the SiO2 substrate by thermal evaporation, then deposit SiO2 by electron beam evaporation, and finally prepare a TiO2 film by atomic layer deposition; Step S2: Spin-coat a photoresist with a set thickness on the surface of the bottom high-reflection film obtained in Step S1, and then spin-coat a conductive adhesive with a set thickness; among them, the spin-coating parameters of the conductive adhesive are set as follows: the rotation speed is 4000 - 5000 r / min, and the thickness is 30 - 50 nm; baking is carried out using a hot plate, the temperature is 87 - 93 °C, and the time is 1.8 - 2.2 minutes; Step S3: Expose the photoresist in Step S2 using electron beam direct writing gray-scale lithography technology, and after development, obtain photoresist spacer layers with different heights; among them, the exposed areas correspond one-to-one with the shapes of the sensor pixels; Step S4: On the photoresist spacer layers with different heights prepared in Step S3, prepare a top high-reflection film by ion beam sputtering deposition technology according to the method of Step S1 to obtain a metal-dielectric hybrid material FP cavity filter array structure.

2. The method according to claim 1, characterized in that, The photoresist in Step S2 is PMMA photoresist.

3. The method according to claim 1, wherein The thickness of the photoresist in Step S2 is controlled by the rotation speed of the spin coater.

4. The method according to claim 1, wherein The spin-coating parameters of the photoresist in Step S2 are set as follows: the rotation speed is 2000 - 3000 r / min, and the thickness is 500 - 650 nm; baking is carried out using a hot plate, the temperature is 178 - 182 °C, and the time is 8 - 12 minutes to cure it.

5. The method according to claim 1, characterized in that, In Step S3, the photoresist in Step S2 is exposed using electron beam direct writing gray-scale lithography technology, and after development, photoresist spacer layers with different heights are obtained. Specifically: The exposure parameters are set as follows: the beam spot current is 9.8 - 10.2 nA, the beam spot size is 15 - 25 nm, and the exposure dose is 150 μC / cm2 - 250 μC / cm2; the thickness of the photoresist spacer layer is controlled by the exposure dose and development parameters; The development parameters are set as follows: after exposure, first rinse off the conductive adhesive with deionized water for 0.5 - 1 minute; Then carry out development. The developer is a mixed solution of isopropyl alcohol and deionized water, and the mixing ratio is 1:

1. The development temperature is 22.8 °C - 23.2 °C, and the development time is 4 - 5 minutes; rinse in deionized water for 0.5 - 1 minute.

Images