| The thermopile infrared(IR)detectors have a series of unique advantages such as no additional bias circuit,no target object movement,wide spectral response,room temperature operation,low power consumption,and great cost performance.With the rapid development of semiconductor technology,thermopile chips have been greatly optimized and opened the door to mass production with the help of complementary metal oxide semiconductor(CMOS)and micro electromechanical system(MEMS)technologies.However,current thermopile chips still have poor IR absorption characteristics in an ultra-wide spectral range,resulting in low detectivity,long time constant,and poor sensitivity.This paper used mathematical analysis to theoretically calculated the main performance parameters of thermopile infrared detectors,and analyzed in detail the influences of the structures and materials of the thermopile infrared detector on its performance parameters.Based on the above theoretical calculation and analysis,the thermopile infrared detectors with interferometric absorber structure,resonant cavity absorber structure and porous absorber coating had been designed and manufactured,and the relationship between material-structure-performance was systematically studied and optimized,and the infrared absorption characteristics of the final device in the ultra-wide spectral range are significantly improved.The main research content and results are as follows:For the life rays of 8-14?m,this paper introduced the design concepts of interference and anti-reflection,and designed and prepared two thermopile chips with different interferometric absorber structures,one absorber structure of which is composed of thermocouple layer(Al),thermopile passivation and protection layers(Si3N4 and Si O2)and antireflection layer(Ge),another absorber structure is only composed of thermocouple layer(Al),thermopile passivation and protection layers(Si3N4 and Si O2).Analytical calculations and simulation results showed that the average absorptance of the modified interferometric absorber structure with Ge anti-reflection layer is?86.47%at 8-14?m,?25%higher than that of the reference interferometric absorber structure.In the entire design process of the two thermopile chips with different interferometric absorber structures,the Al layer plays a key role because it not only serves as the thermopile and the connection layer between thermocouples,but also as the reflector for the incident infrared light at the bottom of absorber structure.Al layer can not only form optical interference to enhance absorptance,but also quickly conduct the heat of absorber to the hot junctions.In order to realize that a detector can be applied to various fields such as CO2,CO,N2O and CH4 gas detection and non-contact human body temperature detection,the device is required to have an ultra-wide absorption spectrum.So,this paper designed a thermopile infrared detector with resonant cavity absorber structure.The designed resonant cavity absorber structure used Al as the bottom reflective metal layer,air as the intermediate dielectric layer,and Si O2/Ti N/Si3N4sandwich layers as the top absorption metal layer.The designed resonant cavity absorber structure exhibited 89.56%and 93.51%average absorptance at 3-5?m and 8-14?m,respectively.Meanwhile,in the entire design process of the thermopile chip with resonant cavity absorber structure,the bottom reflective metal(Al)was designed to be deposited on the cold junctions of the thermopile.Due to this design,Al not only acted as the reflective metal layer of the resonant cavity absorber structure to reflect the infrared radiation from the cold junctions and form the resonant cavity absorber structure to enhance the infrared absorption of the top absorption metal layer,but also avoided the cold junctions to absorb infrared radiation,suppressed the temperature rise of the cold junctions,increased temperature difference between the hot and cold junctions,and improved the responsivity and detectivity of the thermopile infrared detector.This paper proposes that the electrostatic spraying method is used for the preparation of infrared absorption coatings,which has the advantages of simple process,wide absorption spectrum,and suitable for mass production.A high-voltage electrostatic sprayer was built,and the carbon nanoparticles(CNP),Si3N4 and Ti N nanoparticles loaded porous structure carbon microparticles(CMP)coating(CMP/CNP-Si3N4-Ti N)as broadband light superabsorber was prepared.The framework of CMP/CNP-Si3N4-Ti N coating was made up of CMP stacked on each other,and the CNP,Si3N4 and TiN nanoparticles were attached to the CMP surface,forming a large number of dendritic structures.Benefited from the synergetic effect of CMP,CNP,Si3N4and Ti N,the CMP/CNP-Si3N4-Ti N coating can create guided mode for manipulation of incident light waves and provide multiple reflections and scatterings,which can obstruct the escape of incident light waves,made the light propagation path increase,and increase the contact of the coating with light.Finally,the CMP/CNP-Si3N4-Ti N coating exhibited 93.8%and 92.6%absorption at 3-5?m and 8-14?m,respectively.This paper designed and prepared a 5.5?m long wave-pass filter with great optical characteristics,low film sensitivity,great mechanical properties and process stability for non-contact human body temperature detection.The thermopile chip and optical filter designed and developed above are used to prepare the thermopile detector device through the packaging process.The detection results show that the responsivity and specific detectivity of the reference thermopile infrared detector are?256.6 VW-1 and 1.47×108 cm Hz1/2W-1,while those of the modified thermopile infrared detector with Ge anti-reflection layer arrive at?302.3 VW-1 and1.73×108 cm Hz1/2W-1,which increase by?18%.The responsivity and specific detectivity of the modified thermopile infrared detector with CMP/CNP-Si3N4-Ti N coating are?417 VW-1 and2.39×108 cm Hz1/2W-1,which was 62.5%higher than that of the reference thermopile infrared detector. |
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