The Structure Design And Manufacture Research Of A Thermopile IR Detector Based On MEMS Process

In present society, the IR（infrared radiation） detector plays a more and more importantrole in both military and civil domain. With the introduction of MEMS（Micro-Electro-Mechanical Systems） process to IR technology in 1980’s , the thermopileinfrared detector, as a kind of uncooled IR detector, has directed to some IC compatible typesbased on silicon which have caused lots of attentions for the advantages of low cost, lowenergy consumption and miniaturization comparing with the conventional device. However,there are a lot of disadvantages in the design and IC compatibility of resent research. In thedissertation, some innovations on structure and IC compatibility are put forward to integratethe detector. Accordding to lots of process experiments, a new thermopile infrared detectorwhich is fabricated simplily and CMOS compatible is obtained.The design has some research spots more excellent than conventional thermopile IRdetector:（1） In the theory and design, there are some innovation spots for the cost and IC compatibility,including: To break the Silicon substrate’limitation to release and save the price of SOI, anew substrate structure which has the polysilicon on the SiO2layer （Si-SiO₂-POLY） ispresent; The two materials of thermocouple are terrace and insulated by LPCVD siliconoxide so that the place is saved. The stationary heat model is built to analyze the device.Establish the detector’s size and influences of absorbing area。（2） In the process, analyses the MEMS process in the detector’s structure designed and dosome experiments make sure the design is IC compatible, including: when dry etching ofpolysilicon quirk（GT 2μm）,the relationship between the factor of etching and the patternand size of sidewall; after filling the quirk with silicon oxide, the condition of surface test; structure formation in the deep and narrow hole and the XeF₂dry etching condition etc.Besides, analyse and explain the experimental results.（3） In addition, the thesis presents a needle-like array ofα-Si which appears in halogen gasdry etching as the absorbing material on the surface. According to change the etchingcondition, a series of sample wafers are achieved. Testing and checking the IRabsorptivity of these samples under different wavelength light source.Accordding to comparing the process fabrication condition, several groups of samplesare obtained in different experiments, the whole wafer’s surface or sidewall pattern after breakoff the wafer are tested by SEM. After analyse the test results, the feasibility of theinnovation spots in the design in the process fabrication is proved. Based on it, the completefabrication process is integrated to make a whole fabrication flow of the thermopile infrareddetector which has self-stopping in etching polysilicon to release the device.