An infrared dual-color detector coupled with a silicon super-hemisphere lens and a preparation method thereof

Abstract

The application relates to an infrared dual-color detector coupled with a silicon super-hemisphere lens and a preparation method thereof. ‑6 The infrared dual-color detector coupled with the silicon super-hemisphere lens breaks through the 10~14 mu m and 16~24 mu m dual-band absorption bottleneck by combining manganese-cobalt-nickel oxygen (MCNO) material and the synergistic effect of the phonon absorption of Si3N4 and the free carrier absorption of an ultrathin metal bismuth (Bi) absorption layer; the device adopts silicon super-hemisphere lens convergence, infrared anti-reflection layer optimization of light-heat conversion, and cooperates with a vacuum packaging process to realize room-temperature high-sensitivity detection. The detector has non-refrigeration, wide spectral response and micro-electro-mechanical system (MEMS) process compatibility, and is suitable for fields such as gas detection and long-wave-very long-wave infrared spectrum measurement.

Description

Technical Field

[0001] This invention relates to the field of infrared detector technology, specifically to a silicon hemispherical lens-coupled infrared dual-color detector and its fabrication method. More specifically, it utilizes a silicon hemispherical lens to focus and enhance the incident power density, combining a metallic Bi thin film absorption layer and an MCNO thermistor thin film layer to achieve high absorption of dual-color infrared at 10~14μm and 16~24μm respectively, and combining a composite microbridge structure and vacuum encapsulation to achieve a low thermal conductivity and high detection sensitivity infrared dual-color uncooled detector. Background Technology

[0002] MCNO (Mn-Co-Ni-O, manganese cobalt nickel oxide) is a typical thermistor material, widely used in both military and civilian infrared detection due to its high negative temperature coefficient of resistance (approximately -4% / ℃ at room temperature) and strong stability (capable of stable operation in near-Earth orbit for over 10 years). This material achieves infrared signal conversion through a photothermal effect. Its performance stability, adjustable resistivity, and compatibility with MEMS processes make it an ideal material for uncooled detection applications in fields such as Earth resource exploration and atmospheric remote sensing. In these applications, detectors need high absorption efficiency in the 10–14 μm and 16–24 μm ranges. However, MCNO materials face several technical bottlenecks in practical applications: insufficient absorption in the long-wave infrared band; in the 10–14 μm atmospheric window, the intrinsic absorption of a 10 μm thick MCNO film is only 10–30%, limiting the photothermal conversion efficiency and resulting in insufficient detector responsivity. Long-wave infrared reflection loss is significant. In the 16–24 μm band, MCNO materials exhibit strong phonon resonance peak absorption, but due to their high refractive index (n≥3) and extinction coefficient (k≥1), reflection loss of approximately ~40% or more can occur at the air / material interface, reducing the overall absorption efficiency to 40–50%. .

[0003] Therefore, overcoming the drawback of low intrinsic absorption of MCNO thermistor thin film materials in the 10~14μm and 16~24μm bands has become a technical problem that needs to be solved in the development of high-performance long-wavelength dual-color uncooled detectors.

[0004] References

[0005] [1] Zhang Leibo, Hou Yun, Zhou Wei, Huang Zhiming, Chu Junhao. Development of a manganese cobalt nickel oxide thin film thermistor-type multi-element infrared detector. Journal of Infrared and Millimeter Waves, 2014, 33(4): 359-363;

[0006] [2]L. He, Z. Ling. Studies of temperature dependent ac impedance of anegative temperature coefficient Mn-Co-Ni-O thin film thermistor. AppliedPhysics Letters, 2011, 98(24): 242112;

[0007] [3]Z. Huang, W. Zhou, C. Ouyang, J. Wu, F. Zhang, J. Huang, et al.High performance of Mn-Co-Ni-O spinel nanofilms sputtered from acetateprecursors. Scientific Reports, 2015, 5(1): 10899;

[0008] [4]W. Zhou, L. Zhang, C. Ouyang, J. Wu, Z. Huang, X. feng Xu. Microstructural, electrical and optical properties of highly (220) oriented spinelMn–Co–Ni–O film grown by radio frequency magnetron sputtering. AppliedSurface Science, 2014, 311: 443-447;

[0009] [5]R. Dannenberg, S. Baliga, R. J. Gambino, A. H. King, A. P. Doctor.Infrared optical properties of Mn 1.56 Co 0.96 Ni 0.48 O4 spinel films sputterdeposited in an oxygen partial pressure series. Journal of Applied Physics,1999, 86(5): 2590-2601;

[0010] [6] Zhang Zhibo, Wang Ding, Qiu Qinqian, Gao Yanqing, Zhou Wei, Huang Zhiming. Ultraviolet-far-infrared broadband NiMn2O4 and Mn 1.56 Co 0.96 Ni 0.48 Study on optical properties of O4. Journal of Infrared and Millimeter Waves, 2020, 39(1): 65-71. Summary of the Invention

[0011] The purpose of this invention is to propose an infrared dual-color detector coupled with a silicon hemispherical lens and its fabrication method. By leveraging the synergistic effect of Bi free carrier absorption in the metal Bi thin film absorption layer and the lattice vibration peaks in the Si3N4 isolation layer (e.g., two layers of silicon nitride) and the MCNO thermistor layer, combined with the low thermal conductivity support structure of the Si3N4-Si-Si3N4 composite microbridge layer, silicon hemispherical lens focusing, and vacuum packaging technology, the invention overcomes the problem of low absorption efficiency of MCNO single material in the 10~14μm and 16~24μm wavelength bands, achieving high-sensitivity mid-to-long-wavelength dual-color infrared detection under low-voltage bias.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is: an infrared dual-color detector coupled with a silicon hemispherical lens, characterized in that: the infrared dual-color detector includes a detector element, which includes a silicon substrate, a microcavity structure, a Si3N4-Si-Si3N4 composite microbridge layer, an MCNO thermistor layer, a Si3N4 isolation layer, a metal Bi thin film absorption layer, an external metal electrode layer Ti / Au, and metal leads;

[0013] A microcavity structure is fabricated on a silicon substrate, and on the silicon substrate are sequentially a Si3N4-Si-Si3N4 composite microbridge layer, an MCNO thermistor layer, a Si3N4 isolation layer, and a metal Bi thin film absorption layer covering the microcavity structure.

[0014] External metal electrode layers Ti / Au are fabricated at both ends of the MCNO thermistor material layer to serve as positive and negative power supply electrodes and signal terminals; the external metal electrode layers Ti / Au are connected to metal leads.

[0015] Furthermore, the infrared dual-color detector also includes an infrared anti-reflection layer, a silicon hemispherical mirror, a PCB circuit board and electrical signal transmission lines, a solder ball, a flange, external leads, a copper tube housing, a copper tube housing cover plate, a copper tube, and sealant.

[0016] The silicon substrate of the detector is back-attached to the center of the silicon hemispherical lens coated with an infrared anti-reflection layer, and the silicon hemispherical lens is glued and encapsulated onto a copper tube cover plate with a PCB circuit board and electrical signal transmission line. The metal leads are connected to the PCB circuit board in the PCB circuit board and electrical signal transmission line. The PCB circuit board and electrical signal transmission line sequentially lead out the electrical signal through the solder ball, flange and external lead.

[0017] The copper tube is connected to the opening of the copper tube housing and the copper tube housing cover plate. The opening of the copper tube is sealed with sealant to achieve vacuum encapsulation of the detector element.

[0018] Furthermore, the microcavity structure has a size of 100~300 μm square and a depth of 10~20 μm;

[0019] The Si3N4-Si-Si3N4 composite microbridge layer includes Si3N4, Si, and Si3N4 films with thicknesses of 0.3 μm, 0.1 μm, and 0.3 μm.

[0020] Furthermore, the thickness of the MCNO thermistor layer is 1.2 μm;

[0021] The thickness of the metallic Bi thin film absorber layer is 0.1 μm.

[0022] Furthermore, the thicknesses of the external metal electrode layers Ti and Au are 30 nm for Ti and 100 nm for Au, respectively.

[0023] A method for fabricating a silicon hemispherical lens coupled infrared dual-color detector, the specific steps of which are as follows:

[0024] Step 1: Prepare a porous silicon sacrificial layer. A low-doped, single-sided polished P-type (100) high-resistivity silicon substrate is selected as the silicon substrate and placed in a mixed solution of hydrofluoric acid and ethanol to prepare a porous silicon sacrificial layer with a diameter of 100~300 μm and a depth of 10~20 μm.

[0025] Step 2: A Si3N4-Si-Si3N4 composite microbridge layer was prepared using plasma-enhanced chemical vapor deposition. Si3N4, Si, and Si3N4 films with thicknesses of 0.3 μm, 0.1 μm, and 0.3 μm were sequentially prepared on a silicon substrate and a porous silicon surface using plasma-enhanced chemical vapor deposition, thereby obtaining the Si3N4-Si-Si3N4 composite microbridge layer.

[0026] Step 3: Magnetron sputtering deposition of MCNO thermistor material layer. An RF magnetron sputtering system was used to prepare the MCNO thermistor film layer. Before sputtering, the silicon substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water. After cleaning, the substrate was rapidly annealed in a rapid annealing furnace. An MCNO thin film was prepared by sputtering deposition using an MCNO polycrystalline target in a pure argon atmosphere. The prepared film was annealed in an annealing furnace and then removed, finally obtaining a 1.2 μm thick MCNO thermistor material layer.

[0027] Step 4: Fabrication of Si3N4 isolation layer. A 0.03 μm thick Si3N4 isolation layer is prepared by plasma-enhanced chemical vapor deposition.

[0028] Step 5: Fabricate a metal Bi thin film absorption layer. A dual-ion beam sputtering system is used to prepare a metal Bi thin film absorption layer above the Si3N4 isolation layer region. Finally, a metal Bi thin film absorption layer with a thickness of 0.1 μm is deposited.

[0029] Step 6: Deposit the external metal electrode layer Ti / Au. Using ultraviolet lithography, expose the positive and negative supply electrodes and signal terminals at both ends of the MCNO thermistor material layer. Deposit the external metal electrode layer Ti / Au by dual ion beam sputtering. The thickness of the prepared external metal electrode layer Ti / Au is set to Ti: 30 nm and Au: 100 nm, respectively.

[0030] Step 7: Etching the porous silicon sacrificial layer to form a microcavity structure. The porous silicon sacrificial layer is etched using a 1% (wt) KOH solution with a small amount of ethanol added. After etching, a microcavity structure is formed. The sample is rinsed multiple times with deionized water, and then immersed in a solution of ethanol and isopropanol with low surface tension to replace the remaining deionized water in the microcavity structure, thus avoiding excessive surface tension that could cause the adhesion and collapse of the Si3N4-Si-Si3N4 composite microbridge layer.

[0031] Step 8: Encapsulation and Spot Welding. The silicon substrate is back-attached to the center of the silicon hemispherical lens coated with an infrared antireflection layer. The silicon hemispherical lens is then glued and encapsulated onto a copper tube cover plate containing a PCB circuit board and electrical signal transmission lines. Using an ultrasonic spot welder, the external metal electrode layer Ti / Au is connected to the PCB circuit board via metal leads. The electrical signals of the device are then led out through welding balls, flanges, and external leads. Copper tubes are then connected to the openings of the copper tube base and the copper tube cover plate. The openings of the copper tubes are sealed with sealant to perform vacuum encapsulation of the device, completing the fabrication of the silicon hemispherical lens-coupled infrared dual-color detector.

[0032] Furthermore, in step one, the resistivity of the silicon substrate is 0.1~1 Ω·cm;

[0033] The ratio of HF to ethanol in the mixed solution is HF:CH3CH2OH = 1:1;

[0034] The initial anodizing current density is 10 mA / cm². 2 Increased to 50 mA / cm after 2 minutes 2 Oxidation time: 5 min.

[0035] Furthermore, in step three, the silicon substrate is ultrasonically cleaned for 5 minutes each with acetone, anhydrous ethanol and deionized water before sputtering.

[0036] The rapid annealing furnace performs rapid annealing treatment on the substrate at a temperature of 350℃ for 5 minutes;

[0037] MCNO thin films were prepared by sputtering deposition using a polycrystalline MCNO target under a pure argon atmosphere. The preparation parameters were as follows: substrate temperature 200–450 °C, sputtering power 50 W, and base vacuum 9 × 10⁻⁶. -8 Torr, sputtering pressure of 3 mTorr, sputtering gas of pure Ar, sputtering time of 160 h;

[0038] The MCNO film was placed in an annealing furnace and annealed in air at 450 °C for 20 min.

[0039] Furthermore, in step five, a metal Bi thin film absorber layer is prepared using a dual ion beam sputtering system. The preparation process parameters are as follows: sputtering pressure is 0.2 mTorr, sputtering energy is 800 eV, and sputtering time is 10 min.

[0040] Furthermore, in step seven, the corrosion time is 3 minutes.

[0041] In view of the above technical features, the present invention has the following beneficial effects:

[0042] 1. This invention discloses a silicon hemispherical lens-coupled infrared dual-color detector. It leverages the free carrier absorption characteristics of an ultrathin metal thin film (i.e., a Bi metal thin film absorption layer) and the lattice vibration peaks of manganese cobalt nickel oxide (i.e., the MCNO thermistor material layer) to achieve synergy with the focusing effect of the silicon hemispherical lens, thereby enhancing the photothermal conversion efficiency in the 10–14 μm and 16–24 μm (semi-transparent window) bands. This achieves high absorption efficiencies of 70% on average and 80% and 75% on peak values ​​for these two bands, respectively. This effectively solves the problems of near-transparency of MCNO thermistor materials in the 10–14 μm band and the weak absorption of thermistors such as vanadium oxide and amorphous silicon in the very long wavelength infrared (VLS) bands. This invention overcomes the low absorption efficiency of MCNO single materials in the 10–14 μm and 16–24 μm bands, effectively improving the wide-band light absorption of MCNO devices and enabling its application in array detectors. The dual-color detector based on this design is expected to be applied in gas detection, long-wave to very long-wave infrared spectroscopy measurement, security monitoring, and other fields, with broad market application prospects.

[0043] 2. The present invention provides an infrared dual-color detector coupled with a silicon hemispherical lens, which utilizes a silicon nitride-silicon-silicon nitride composite microbridge low thermal conductivity support structure (thermal conductivity ≤ 10). -6The W / K (Si3N4-Si-Si3N4 composite microbridge layer) combines the synergistic effect of phonon absorption by the manganese cobalt nickel oxide (MCNO thermistor layer) material and the Si3N4 isolation layer with the free carrier absorption by the ultrathin bismuth (Bi thin film absorption layer) absorption layer, breaking through the absorption bottleneck of the 10~14μm and 16~24μm dual-band bands. The device uses a silicon hemispherical lens for focusing and an infrared antireflection layer to optimize photothermal conversion, combined with vacuum packaging technology to achieve high-sensitivity detection at room temperature. This detector features uncooled operation, wide spectral response, and microelectromechanical systems (MEMS) process compatibility, making it suitable for gas detection, long-wavelength to very long-wavelength infrared spectroscopy measurements, and other fields.

[0044] 3. This invention discloses a silicon hemispherical lens-coupled infrared dual-color detector. It utilizes the superposition of Si3N4 and MCNO lattice vibration peaks with the free carrier absorption of an ultrathin Bi metal film to enhance long-wave infrared absorption in the sensing element. Combined with silicon hemispherical lens focusing, a microbridge structure (i.e., a microbridge structure formed by a Si3N4-Si-Si3N4 composite microbridge layer and a microcavity structure) design, and vacuum packaging to reduce device thermal conductivity, the device's response sensitivity under low-voltage bias is synergistically optimized. The new device can be used for uncooled infrared detection in 10~14μm and 16~24 μm dual-band infrared fields, meeting the application requirements in gas detection, long-wave infrared dual-color spectroscopy measurement, and other fields. Attached Figure Description

[0045] Figure 1 This is a side view of the infrared dual-color detector structure coupled with a silicon hemispherical lens in specific embodiment 1.

[0046] Figure 2 This is a top view of the infrared dual-color detector structure coupled with a silicon hemispherical lens in specific embodiment 1.

[0047] Figure 3 The images show partial schematic diagrams and enlarged views of the detector silicon hemispherical lens and microbridge structure device sensing element (i.e., detector element 4) in specific embodiment 1.

[0048] Figure 4 This is a schematic diagram of the fabrication process of the infrared dual-color detector coupled with a silicon hemispherical lens in Specific Embodiment 1.

[0049] Figure 5 The calculation results of the CODE thin film design software for the absorption spectrum of the infrared dual-color detector in Specific Embodiment 1 are shown.

[0050] In the diagram: 1. Infrared antireflection layer;

[0051] 2. Silicon super-hemispherical mirror;

[0052] 3-1. Silicon substrate; 3-2. Porous silicon sacrificial layer; 3-3. Microcavity structure;

[0053] 4. Detector element; 4-1. Si3N4-Si-Si3N4 composite microbridge structure; 4-2. MCNO thermistor layer; 4-3. Si3N4 isolation layer; 4-4. Metal Bi thin film absorption layer;

[0054] 5. External metal electrode layer Ti / Au;

[0055] 6. Metal leads;

[0056] 7. PCB circuit boards and electrical signal transmission lines;

[0057] 8. Welded balls;

[0058] 9. Flange;

[0059] 10. External leads;

[0060] 11-1 Copper tube housing seat; 11-2 Copper tube housing cover plate;

[0061] 12-1. Sealant;

[0062] 13. Copper pipe. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings.

[0064] Based on the above structure, an embodiment detector was fabricated:

[0065] See Figures 1 to 5 Specific embodiment 1 provides a silicon hemispherical lens coupled infrared dual-color detector, including a detector element 4. The detector element 4 includes a silicon substrate 3-1 (e.g., a high-resistivity silicon substrate), a Si3N4-Si-Si3N4 composite microbridge layer 4-1, an MCNO thermistor layer 4-2, a Si3N4 isolation layer 4-3, a metal Bi thin film absorption layer 4-4, and metal leads 6. The device structure can be specifically described as follows: a microcavity structure 3-3 is fabricated on the silicon substrate 3-1, a Si3N4-Si-Si3N4 composite microbridge layer 4-1 is fabricated on top, an MCNO thermistor layer 4-2 is then fabricated on top, a Si3N4 isolation layer 4-3 is fabricated on the MCNO thermistor layer 4-2, a metal Bi thin film absorption layer 4-3 is then fabricated, and finally, external metal electrode layers Ti / Au5 are fabricated at both ends of the MCNO thermistor layer 4-2 as positive and negative supply electrodes and signal terminals, respectively. The external metal electrode layers Ti / Au5 are connected to the metal leads 6.

[0066] The infrared dual-color detector also includes an infrared anti-reflection layer 1, a silicon hemispherical mirror 2, a PCB circuit board and electrical signal transmission line 7, a solder ball 8, a flange 9, an external lead wire 10, a copper tube housing 11-1, a copper tube housing cover plate 11-2, a copper tube 13, and sealant 13.

[0067] The silicon substrate 3 of the detector element 4 is back-attached to the center of the silicon hemispherical lens 2 coated with infrared antireflection layer 1, and the silicon hemispherical lens 2 is glued and encapsulated onto the copper tube cover plate 11-2 with PCB circuit board and electrical signal transmission line 7 (for example, the silicon hemispherical lens 2 is glued and encapsulated onto the copper tube cover plate 11-2 with epoxy resin 12-2 to ensure a sealed connection between the two). The metal lead 6 is connected to the PCB circuit board in the PCB circuit board and electrical signal transmission line 7. The PCB circuit board and electrical signal transmission line 7 sequentially lead out the electrical signal through the solder ball 8, flange 9 and external lead 10.

[0068] The copper tube 13 is connected to the opening of the copper tube housing 11-1 and the copper tube housing cover plate 11-2. The opening of the copper tube 13 is sealed with sealant 13 to achieve vacuum encapsulation of the detector element 4.

[0069] The microcavity structure 3-3 has dimensions of 100–300 μm square and a depth of 10–20 μm. The Si3N4-Si-Si3N4 composite microbridge layer 4-1 includes Si3N4, Si, and Si3N4 films with thicknesses of 0.3 μm, 0.1 μm, and 0.3 μm, respectively. The MCNO thermistor layer 4-2 has a thickness of 1.2 μm. The metal Bi thin film absorber layer 4-4 has a thickness of 0.1 μm. The external metal electrode layer Ti / Au5 has thicknesses of 30 nm for Ti and 100 nm for Au.

[0070] This embodiment 1 describes a method for fabricating an infrared dual-color detector coupled with a silicon hemispherical lens.

[0071] Step 1 (S1): Preparation of a porous silicon sacrificial layer 3-2. A low-doped, single-sided polished P-type (100) high-resistivity silicon substrate was selected as the silicon substrate 3-1, with a resistivity of 0.1~1 Ω·cm. It was placed in a mixed solution of HF (hydrofluoric acid) and ethanol with a ratio of HF:CH3CH2OH=1:1. The initial anodic oxidation current density was 10 mA / cm. 2 Increased to 50 mA / cm after 2 minutes 2 An oxidation time of 5 min was used to prepare a porous silicon sacrificial layer 3-2 with a diameter of 100-300 μm and a depth of 10-20 μm.

[0072] Step 2 (S2): The Si3N4-Si-Si3N4 composite microbridge layer 4-1 is prepared using plasma-enhanced chemical vapor deposition (PECVD). Si3N4, Si, and Si3N4 films with thicknesses of 0.3 μm, 0.1 μm, and 0.3 μm are sequentially prepared on a silicon substrate and a porous silicon surface using PECVD, thereby obtaining the Si3N4-Si-Si3N4 composite microbridge layer 4-1.

[0073] Step 3 (S3): Magnetron sputtering deposition of MCNO thermistor layer 4-2. An MCNO thermistor film layer was prepared using a LAB Line SPUTTER 5 RF magnetron sputtering system manufactured by Kurt J. Lesker, USA. Before sputtering, the silicon substrate 3-1 was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water for 5 minutes each. After cleaning, the substrate was rapidly annealed in a rapid annealing furnace (350℃, 5 min). An MCNO thin film was prepared by sputtering deposition using an MCNO polycrystalline target under a pure argon atmosphere. The process parameters were: substrate temperature 200~450℃, sputtering power 50 W, and base vacuum 9×10⁻⁶. -8 The sputtering pressure was 3 mTorr, the sputtering gas was pure Ar, and the sputtering time was 160 h. The prepared film was placed in an annealing furnace under atmospheric conditions and annealed in air at 450 °C for 20 min before being removed, finally yielding a 1.2 μm thick MCNO thermistor material layer 4-2.

[0074] Step 4 (S4): A 0.03 nm thick Si3N4 isolation layer is fabricated using plasma-enhanced chemical vapor deposition (PECVD).

[0075] Step 5 (S5): Fabrication of the Bi thin film absorber layer 4-4. Using the AD-IBSD1010 dual-ion beam sputtering system from Beijing Advanced Ion Beam Technology Co., Ltd., a 0.1 μm thick Bi thin film absorber layer 4-4 was deposited on the window above the Si3N4 isolation layer 4-3 using a dual-ion beam. The fabrication parameters for the Bi thin film absorber layer using the dual-ion beam sputtering system were as follows: sputtering pressure 0.2 mTorr, sputtering energy 800 eV, and sputtering time 10 min.

[0076] Step Six (S6): Deposit the external metal electrode layer Ti / Au5. Using ultraviolet lithography, expose the positive and negative supply electrodes and signal terminals at both ends of the MCNO thermistor material layer 4-2. Then, deposit the external metal electrode layer Ti / Au5 using dual-ion beam sputtering. The thicknesses of the prepared external metal electrode layer Ti / Au5 are set to Ti: 30 nm and Au: 100 nm, respectively.

[0077] Step 7 (S7): Etch the porous silicon sacrificial layer 3-2 to form the microcavity structure 3-3. Etch the porous silicon sacrificial layer 3-2 using a 1% (wt) KOH solution with a small amount of ethanol added for 3 minutes. After etching, the microcavity structure 3-3 is formed. Rinse repeatedly with deionized water, then immerse the sample in a solution of ethanol and isopropanol with low surface tension to replace the remaining deionized water in the microcavity structure 3-3, preventing excessive surface tension from causing the adhesion and collapse of the Si3N4-Si-Si3N4 composite microbridge layer 4-1.

[0078] Step 8 (S8): Encapsulation and Spot Welding. The silicon substrate 3-1 is back-attached to the center of the silicon hemispherical lens 2 coated with the infrared antireflection layer 1, and the silicon hemispherical lens 2 is then attached and encapsulated onto the copper tube cover plate 11-2, which includes a PCB circuit board and electrical signal transmission lines 7. Using an ultrasonic spot welder, the external metal electrode layer Ti / Au5 is connected to the PCB circuit board via metal leads 6, and the electrical signals of the device are led out via welding balls 8, flanges 9, and external leads 10. Then, copper tubes 13 are connected to the openings of the copper tube base 11-1 and the copper tube cover plate 11-2, and the openings of the copper tubes 13 are sealed with sealant 13 to perform vacuum encapsulation of the device, completing the fabrication of the silicon hemispherical lens-coupled infrared dual-color detector.

[0079] In this embodiment 1, a silicon hemispherical lens-coupled infrared dual-color detector achieves over 70% absorption of the photosensitive element for 10-14 μm and 16-24 μm. This invention effectively improves the broadband light absorption efficiency of MCNO devices and can be applied to array detector devices.

[0080] Theoretical calculations show that the silicon super-hemispherical microbridge bismuth film structure of the present invention, through the synergistic effect of free carrier absorption of bismuth film and vibration peak of manganese cobalt nickel oxygen lattice, combined with silicon super-hemispherical lens focusing and vacuum packaging technology, improves the average absorption of the detector in 10~14 μm and 16~24 μm to more than 70%.

[0081] The above examples are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any modifications or changes made to the above embodiments without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An infrared dual-color detector coupled with a silicon hemispherical lens, characterized in that: The infrared dual-color detector includes a detector element (4), which includes a silicon substrate (3-1), a microcavity structure (3-3), a Si3N4-Si-Si3N4 composite microbridge layer (4-1), an MCNO thermistor layer (4-2), a Si3N4 isolation layer (4-3), a metal Bi thin film absorption layer (4-4), an external metal electrode layer Ti / Au (5), and metal leads (6). A microcavity structure (3-3) is fabricated on a silicon substrate (3-1). Above the silicon substrate (3-1) are, in sequence, a Si3N4-Si-Si3N4 composite microbridge layer (4-1), an MCNO thermistor layer (4-2), a Si3N4 isolation layer (4-3), and a metal Bi thin film absorber layer (4-4) covering the microcavity structure (3-3). External metal electrode layers Ti / Au (5) are prepared at both ends of the MCNO thermistor material layer (4-2) as positive and negative power supply electrodes and signal terminals; the external metal electrode layers Ti / Au (5) are connected to metal leads (6).

2. The infrared dual-color detector coupled with a silicon hemispherical lens according to claim 1, characterized in that: The infrared dual-color detector also includes an infrared anti-reflection layer (1), a silicon super-hemisphere mirror (2), a PCB circuit board and electrical signal transmission line (7), a solder ball (8), a flange (9), an external lead wire (10), a copper tube housing (11-1), a copper tube housing cover plate (11-2), a copper tube (13), and sealant (12-1). The silicon substrate (3-1) of the detector element (4) is back-attached to the center of the silicon super-hemispherical lens (2) coated with an infrared anti-reflection layer (1), and the silicon super-hemispherical lens (2) is glued and encapsulated on a copper tube shell cover plate (11-2) with a PCB circuit board and an electrical signal transmission line (7). The metal lead (6) is connected to the PCB circuit board in the PCB circuit board and the electrical signal transmission line (7). The PCB circuit board and the electrical signal transmission line (7) sequentially lead out the electrical signal through the solder ball (8), the flange (9) and the external lead (10). The copper tube (13) is connected to the opening of the copper tube housing (11-1) and the copper tube housing cover plate (11-2). The opening of the copper tube (13) is sealed with sealant (12-1) to achieve vacuum encapsulation of the detector element (4).

3. The infrared dual-color detector coupled with a silicon hemispherical lens according to claim 1, characterized in that: The microcavity structure (3-3) has a size of 100~300 μm square and a depth of 10~20 μm; The Si3N4-Si-Si3N4 composite microbridge layer (4-1) includes Si3N4, Si, and Si3N4 films with thicknesses of 0.3 μm, 0.1 μm, and 0.3 μm, respectively.

4. The infrared dual-color detector coupled with a silicon hemispherical lens according to claim 1, characterized in that: The thickness of the MCNO thermistor layer (4-2) is 1.2 μm; The thickness of the metal Bi thin film absorber layer (4-4) is 0.1 μm.

5. The infrared dual-color detector coupled with a silicon hemispherical lens according to claim 1, characterized in that: The thicknesses of the external metal electrode layers Ti / Au (5) are 30 nm for Ti and 100 nm for Au.

6. A method for fabricating an infrared dual-color detector coupled with a silicon hemispherical lens, comprising the following specific steps: Step 1: Prepare a porous silicon sacrificial layer (3-2). A low-doped, single-sided polished P-type (100) high-resistivity silicon substrate is selected as the silicon substrate (3-1). The substrate is placed in a mixed solution of hydrofluoric acid and ethanol to prepare a porous silicon sacrificial layer (3-2) with a diameter of 100~300 μm and a depth of 10~20 μm. Step 2: A Si3N4-Si-Si3N4 composite microbridge layer was prepared using plasma-enhanced chemical vapor deposition (4-1). Si3N4, Si, and Si3N4 films with thicknesses of 0.3 μm, 0.1 μm, and 0.3 μm were sequentially prepared on a silicon substrate and a porous silicon surface using plasma-enhanced chemical vapor deposition, thereby obtaining the Si3N4-Si-Si3N4 composite microbridge layer (4-1). Step 3: Magnetron sputtering deposition of MCNO thermistor material layer (4-2). An RF magnetron sputtering system was used to prepare the MCNO thermistor film layer. Before sputtering, the silicon substrate was ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water (3-1). After cleaning, the substrate was rapidly annealed using a rapid annealing furnace. An MCNO thin film was prepared by sputtering deposition using an MCNO polycrystalline target under a pure argon atmosphere. The prepared film was then annealed in an annealing furnace under atmospheric conditions and removed, finally yielding a 1.2 μm thick MCNO thermistor material layer (4-2). Step 4: Fabrication of Si3N4 isolation layer (4-3). A 0.03 μm thick Si3N4 isolation layer (4-3) was prepared by plasma-enhanced chemical vapor deposition. Step 5: Fabricate a metal Bi thin film absorption layer (4-4). A metal Bi thin film absorption layer (4-4) is prepared above the Si3N4 isolation layer (4-3) using a dual ion beam sputtering system. Finally, a metal Bi thin film absorption layer (4-4) with a thickness of 0.1 μm is deposited. Step 6: Deposit external metal electrode layer Ti / Au (5). Using ultraviolet lithography, expose the positive and negative supply electrodes and signal terminals at both ends of the MCNO thermistor material layer (4-2). Deposit external metal electrode layer Ti / Au (5) by dual ion beam sputtering. The thickness of the prepared external metal electrode layer Ti / Au (5) is set to Ti: 30 nm and Au: 100 nm, respectively. Step 7: Etch the porous silicon sacrificial layer (3-2) to form a microcavity structure (3-3). Use a 1% (wt) KOH solution with a small amount of ethanol to etch the porous silicon sacrificial layer (3-2). After etching, the microcavity structure (3-3) is formed. Rinse it multiple times with deionized water. Then immerse the sample in an ethanol and isopropanol solution with low surface tension to replace the deionized water remaining in the microcavity structure (3-3) to avoid excessive surface tension causing the adhesion and collapse of the Si3N4-Si-Si3N4 composite microbridge layer (4-1). Step 8: Encapsulation and spot welding. The silicon substrate (3-1) is back-attached to the center of the silicon hemispherical lens (2) coated with infrared antireflection layer (1), and the silicon hemispherical lens (2) is glued and encapsulated onto the copper tube cover plate (11-2) with PCB circuit board and electrical signal transmission line (7). Using an ultrasonic spot welding machine, the external metal electrode layer Ti / Au (5) is connected to the PCB circuit board through metal lead (6), and the electrical signal of the device is led out through the welding ball (8), flange (9), and external lead (10). Then, the copper tube (13) is connected at the opening of the copper tube base (11-1) and the copper tube cover plate (11-2), and the opening of the copper tube (13) is sealed with sealant (12-1) to perform vacuum encapsulation of the device and complete the fabrication of the infrared dual-color detector coupled with silicon hemispherical lens.

7. The method for fabricating an infrared dual-color detector coupled with a silicon hemispherical lens according to claim 6, characterized in that: In step one, the resistivity of the silicon substrate (3-1) is 0.1~1 Ω·cm; The ratio of HF to ethanol in the mixed solution is HF:CH3CH2OH = 1:1; The initial anodizing current density is 10 mA / cm². 2 Increased to 50 mA / cm after 2 minutes 2 Oxidation time: 5 min.

8. The method for fabricating an infrared dual-color detector coupled with a silicon hemispherical lens according to claim 6, characterized in that: In step three, before sputtering, the silicon substrate is ultrasonically cleaned (3-1) for 5 minutes each with acetone, anhydrous ethanol and deionized water respectively. The rapid annealing furnace performs rapid annealing treatment on the substrate at a temperature of 350℃ for 5 minutes; MCNO thin films were prepared by sputtering deposition using a polycrystalline MCNO target under a pure argon atmosphere. The preparation parameters were as follows: substrate temperature 200–450 °C, sputtering power 50 W, and base vacuum 9 × 10⁻⁶. -8 Torr, sputtering pressure of 3 mTorr, sputtering gas of pure Ar, sputtering time of 160 h; The MCNO film was placed in an annealing furnace and annealed in air at 450 °C for 20 min.

9. The method for fabricating an infrared dual-color detector coupled with a silicon hemispherical lens according to claim 6, characterized in that: In step five, a metallic Bi thin film absorber layer is prepared using a dual-ion beam sputtering system. The preparation process parameters are as follows: sputtering pressure is 0.2 mTorr, sputtering energy is 800 eV, and sputtering time is 10 min.

10. The method for fabricating an infrared dual-color detector coupled with a silicon hemispherical lens according to claim 6, characterized in that: In step seven, the etching time is 3 minutes.

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