Infrared Detection Based On Thermal-induced Mechanical Deflection Effect

Infrared radiation detector could convert invisible infrared radiation into visible image and has important application value in many fields, such as military and civilian.In recent years, the thermal imaging technology, which is based on bi-material micro-cantilever focal plane array and optical readout, is successfully introduced into the thermal detection field and widely used.The infrared detection system, which is based on Thermal-induced Mechanical Deflection Effect (TMDE) of bi-material and the optical readout, is raised in this paper. The properties of Si3N4 films which have been employed to prepare infrared absorption layer is researched, and the process of fabricating device is also studied. The results are shown as follows.1) Sensing unit structure of detection is optimized based on the TMDE. The structure of the bi-material micro-cantilever array is proposed with the scale of 120x120 array and device unit size of 40μm×40μm on glass substrates. The infrared radiation absorption is improved by increasing the area of the reflector in using relatively simple structure.2) The influence of the process parameters on performance of Si3N4 films is researched. Through changing the process parameters, such as PECVD rf power, reaction gas ratio, reaction pressure and working temperature, the Si3N4 film presents different stress. The film shows tensile stress as 426MPa with the film thickness of 500nm. By changing the process parameters, such as PECVD rf power, reaction pressure, deposition time, and working temperature, the Si3N4 film with different absorption can be obtained. When the thickness of the film is 500nm, the relative absorption is 3.5. By changing ICP parameters, such as power, bias power, gas component and gas flow, the etching rate of Si3N4 can reach to 336nm/min with Si3N4/ EPG533 selection ratio of 2.05.3) The manufacturing process of device is researched. The sacrificial layer, reflective layer and infrared absorption layer are fabricated by spin-coating, magnetron sputtering and PECVD technology, respectively. Each layer is patterned in using the lithography. The optimizing parameters are as follows:the speed of spin-coating is 3000r/min, and the sputtering power is 200W, and the argon flow is 80mL/min, and the pressure is 2.0Pa during magnetron sputtering. In PECVD process, the temperature is 350℃, and the power is 100W, and the pressure is 70Pa, the SiH4 flow is 40mL/min and N2 flow is 60mL/min.