Ultraviolet anti-reflection film of silicon-based array detector for spectral analysis

Abstract

The invention discloses an ultraviolet light anti-reflection film of a silicon-based array detector for spectral analysis, and belongs to the technical field of optical thin films. The structure of the ultraviolet light anti-reflection film sequentially comprises a silicon-based array chip, a thickness gradient film layer and a matching reflection film stack from bottom to top. Based on the characteristic that a single pixel of an array detector of an imaging spectrometer only detects monochromatic light, the light absorption efficiency corresponding to the monochromatic light is optimized pixel by pixel by using a thickness gradient film layer and a matched reflecting film stack, so that the photoelectric conversion efficiency is more efficient, and the method is particularly suitable for performance optimization of a silicon-based detector for ultraviolet band spectral analysis. The ultraviolet light anti-reflection film provided by the invention can greatly improve the ultraviolet light absorption efficiency of the silicon-based detector, is compatible with the preparation process of the existing silicon-based detector, is simple in film system structure, and is easy to prepare and produce in batches.

Description

Technical Field

[0001] The invention belongs to the technical field of optical films, and in particular relates to an ultraviolet anti-reflection film of a silicon-based array detector used for spectral analysis. Background Art

[0002] Photodetectors use photogenerated carriers to convert optical signals into electrical signals, thereby achieving quantitative measurement of the intensity of optical signals. Silicon-based detectors are currently the mainstream detectors for visible and near-infrared light detection and are one of the best performing detector options. Traditional photodetectors have a wide-band response curve, and their external quantum efficiency depends not only on the internal quantum efficiency of photoelectric conversion, but also on whether the anti-reflection film on the surface can more efficiently improve the effective light absorption rate in a wide band. For some strongly dispersed absorption materials, especially in the anomalous dispersion band, the material reflectivity is very high, and the anti-reflection effect of the broadband anti-reflection film is very poor, making it difficult to achieve efficient light absorption, thereby reducing the photoelectric efficiency of the detector.

[0003] In astronomical observations, especially in space, the ultraviolet band is a very important band. However, current silicon-based detectors generally have the problem of low photoelectric conversion efficiency in the ultraviolet band. This is due to the strong dispersion and anomalous dispersion characteristics of silicon materials in the ultraviolet band. Traditional anti-reflection films are difficult to achieve high-efficiency anti-reflection in a wide band. When silicon-based detectors are used for spectral analysis, the light signal is further weakened after spectral splitting. Coupled with the low photoelectric conversion efficiency of the detector, it will be difficult to accurately measure the ultraviolet spectrum of celestial bodies. In view of the ultraviolet spectral analysis needs of astronomical observations, improving the ultraviolet photoelectric efficiency of silicon-based detectors is a key and urgent technical goal to be achieved. The key lies in improving the effective light absorption efficiency of ultraviolet light. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, namely, the problem of low light absorption efficiency of silicon-based detectors in the ultraviolet band, the purpose of the present invention is to provide an ultraviolet anti-reflection film for a silicon-based array detector for spectral analysis, which can optimize the film structure according to the distribution position of the light wavelength in the silicon-based array detector in the spectrometer, improve the light absorption efficiency, achieve more than 90% absorption in the ultraviolet band, and thereby improve the ultraviolet photoelectric efficiency of the detector.

[0005] In order to achieve the above-mentioned purpose, the technical solution proposed by the present invention is:

[0006] A UV anti-reflection film for a silicon-based array detector for spectral analysis is constructed, characterized in that the structure of the UV anti-reflection film includes a silicon-based array chip, a thickness gradient film layer and a matching reflective film stack from bottom to top; the silicon-based array chip is a photoelectric detection chip using silicon as a light absorption and photoelectric conversion material; the thickness gradient film layer is xH p, x represents thickness, ranging from 0 to 200 nm, and the x value is adjusted according to the wavelength detected by different pixels, and H represents HfO 2 , p represents the physical thickness; the matching reflective film stack has a structure of LH, L is SiO 2 , H is HfO 2 , all are 1 / 4 wavelength optical thickness, and the reference wavelength is 250nm.

[0007] Compared with the prior art, the present invention has the following advantages:

[0008] 1. No need to develop a wide-spectrum anti-reflection film. According to the detection wavelength corresponding to different pixels, the thickness of the gradient film layer is adjusted to achieve anti-reflection optimization, which greatly reduces the reflection loss and improves the light absorption efficiency of the detector.

[0009] 2. The design of matching reflective film stack can achieve good optical admittance matching for the strong dispersion and anomalous dispersion characteristics of silicon materials in the ultraviolet band without the need to make micro-nano structures on the silicon surface, thus reducing the difficulty of developing ultraviolet silicon detectors;

[0010] 3. The reflectivity of silicon materials in the ultraviolet band can be reduced from about 60% to below 10%, achieving more than 90% light absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of the ultraviolet anti-reflection film of the present invention.

[0012] Figure 2 Schematic diagram of the working process of silicon-based array detector in spectrometer.

[0013] Figure 3 Graph showing the variation of reflectivity with thickness x and light wavelength of an example of the present invention.

[0014] Figure 4 The reflection spectrum curves of the ultraviolet anti-reflection film of the example of the present invention with different x values ​​are shown.

[0015] Figure 5 The figure is the optimal x value distribution curve of the ultraviolet anti-reflection film of the example of the present invention at different wavelengths.

[0016] Figure 6 This is a comparison chart of the optimal reflection spectrum of the ultraviolet anti-reflection film of the example of the present invention and the traditional anti-reflection film.

[0017] Markings in the figure: 1-silicon-based array chip, 2-thickness gradient film layer, 3-matching reflective film stack, 4-spectral spectrometer component, 5-incident white light, 6-beam after spectral spectrometry DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and specific examples.

[0019] An ultraviolet anti-reflection film for a silicon-based array detector for spectral analysis, the structure of which is as follows Figure 1 As shown, from bottom to top, it includes a silicon-based array chip 1, a thickness gradient film layer 2, and a matching reflective film stack 3. When the silicon-based array detector is applied to a spectrometer, its working state is as follows: Figure 2 As shown, it can be seen that after the incident white light 5 enters the spectrometer, it is decomposed into light of different wavelengths by the spectral splitting component 4, forming a light beam 6 after spectral splitting. Since the emission angles of light of different wavelengths are different, after convergence and focusing, when the light beam reaches the silicon-based array detector, light of different wavelengths is received by different pixels of the detector. Therefore, in theory, a single pixel of the array detector used for spectral analysis only needs to consider the optimal absorption efficiency of the received single wavelength light. Based on this basic fact, we can use a thickness gradient film layer and a good film system design to achieve the optimized light absorption efficiency of different pixels of the array detector.

[0020] Specific example: In order to verify the advantages of the patented technical solution of the present invention, that is, the light absorption efficiency of the detector can be improved simply by adjusting the thickness of the thickness gradient film at different positions without making micro-nano structures on the silicon surface, the present invention is further explained below with reference to specific examples.

[0021] The specific example selected is the anti-reflection film of silicon-based array detectors for 200-400nm ultraviolet spectral analysis. In space remote sensing, the ultraviolet band plays an irreplaceable role and can be used for earth atmosphere analysis, environmental monitoring, etc. In space astronomical observations, the ultraviolet band can break through atmospheric absorption to study stellar evolution, analyze planetary atmospheres, explore interstellar media, etc. In China's space remote sensing mission, it is necessary to develop a silicon-based array detector for 200-400nm band spectral analysis. The current technical level still has the problem of poor ultraviolet photoelectric efficiency. The reason is that the anti-reflection effect of traditional silicon-based detectors on ultraviolet broadband anti-reflection films is poor, and there is a high loss of reflected light.

[0022] The present invention proposes a solution for developing an anti-reflection film based on coating a thickness gradient film layer 2 and a matching reflective film stack 3 on a silicon-based array chip 1, wherein the thickness gradient film layer 2 is xH p , x represents thickness, ranging from 0 to 200 nm, and the x value is adjusted according to the wavelength detected by different pixels, and H represents HfO 2 , p represents the physical thickness; the structure of the matching reflective film stack 3 is LH, L is SiO 2 , H is HfO 2 , all are 1 / 4 wavelength optical thickness, and the reference wavelength is 250nm.

[0023] Based on this, we can draw a graph showing how the reflectivity of the UV anti-reflection film changes with the thickness x value of the gradient film layer and the wavelength of light, as shown in the figure below: Figure 3 As shown in the figure, it can be seen that when the x value changes from 0 to 70nm, the spectral reflectance valley value can gradually change from a wavelength of 200nm to 400nm, thus providing feasibility for optimizing the pixel absorption efficiency of the silicon-based array detector.

[0024] Furthermore, by selecting discrete x values, the reflectance spectrum curves corresponding to different x values ​​can be plotted, such as Figure 4 As shown, it can be seen that the valley value of the reflection spectrum at different x values ​​is basically close to 0, which means that the optimized single wavelength light absorption efficiency can be close to 100%.

[0025] On the other hand, with the wavelength of the valley value of the spectrum as the horizontal axis and the corresponding x value as the vertical axis, the optimal x value corresponding to the most efficient absorption of different wavelengths can be plotted, such as Figure 5 When actually applied to spectral analysis, we only need to form a thickness gradient film layer 2 on the silicon-based array chip 1 by vacuum coating and using an active mask according to the corresponding relationship between the pixel and the detection wavelength, so as to achieve the optimization of the light absorption of the pixel.

[0026] Based on the residual reflectivity of the detection wavelength after optimization of each pixel, we can draw the optimal reflection spectrum of the array detector used in the spectrometer and compare it with the uncoated anti-reflection coating and the conventional SiO 2 And Si 3 N 4 The reflection spectrum of the silicon-based detector with anti-reflection coating is compared, such as Figure 6 It can be seen that the ultraviolet anti-reflection film of the silicon-based array detector for spectral analysis of the present invention can reduce the ultraviolet light reflectivity of the silicon detector from about 60% to less than 10%, greatly improving the light absorption rate, and the performance is far better than the traditional single uniform thickness medium anti-reflection film.

Claims

1. An ultraviolet anti-reflection film for a silicon-based array detector for spectral analysis, characterized in that: The structure of the ultraviolet anti-reflection film includes, from bottom to top, a silicon-based array chip, a thickness gradient film layer, and a matching reflective film stack; The silicon-based array chip is a photoelectric detection chip using silicon as a light absorption and photoelectric conversion material; The thickness gradient film layer is xHp, where x represents thickness, ranging from 0 to 200 nm, and the x value is adjusted according to the wavelength detected by different pixels, H represents HfO2, and p represents physical thickness; The matching reflective film stack has a structure of LH, where L is SiO2 and H is HfO2, both have an optical thickness of 1 / 4 wavelength, and the reference wavelength is 250nm.

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