A Design Of MEMS Thermoelectric Infrared Detector With Suspending Absorber And Study Of Its Fabrication Methods

Infrared sensor is a type of sensors based on physical properties variation ofsemiconductor materials caused by infrared radiation, and it is one of the key points of theInternet of things technology. With deeply applied into civilian and military fields, thermopileinfrared detector attracts more and more scholars to study on it. Meanwhile, manyresearches are focused on miniaturization, integration and low power consumption, and havegot remarkable achievements. However, problems such as process incompatibility and lowenergy efficiency always disturb the researchers. To resolve above problems, a kind ofthermopile infrared detector with suspension absorber layer is designed and optimized withone-dimensional heat conduction model. The process of detector is highly compatible withstandard CMOS process after process optimizing, and a structure design and preparationmethod of small volume, high energy efficiency, low noise thermopile infrared detector isintroduced in this paper.This study focuses on:(1)Theoretical calculation method: based on correction algorithm of the Seebeckcoefficient, the paper establishes a one-dimensional thermal balance model, meanwhileoptimizes and calculates the performance of the device, and finally determines the optimalmodel sizes.(2)Structure design method: in order to realize the goals of low cost and high energyefficiency, polyimide are used as the sacrificial layer. After selective etching by optimizing theetch conditions, absorption layer is deposited and only the hot end of thermopiles contact withabsorption layer, the rest of absorption layer is suspended above the thermopiles. Also theSOI structure are used to avoid the complexity of etch process and filling process, thermopilesare placed on both side of the symmetry axis of device, and the device is released from frontside with SF6.(3)In addition, to solve the problems of low absorption rate of traditional materials andprocess incompatibility of metal materials, a set of experiences are launched to explore preparation method of black silicon structure of absorption layer and test IR absorption.In conclusion, through comparing and researching with existing thermopile IR detectors,A structure with suspension absorption layer is designed, and results of key processes areobserved by electron microscope. By analyzing test results, high process compatibility andstructure stability are verified. With experiences of dry etching and releasing of polyimidesacrificial layer, and exploratory research of black silicide as absorption layer, process ofthermopile infrared detector with suspension structure is formulated successfully.