Study On Micromachined Reflective Optical Readable Uncooled Infrared Imaging Device

In resent years, with the development of MEMS (Micro-electro-mechanical system),the study on optical readable uncooled infrared imaging devices attracts a lot of attentionsbecause of its no requiring expensive refrigerating apparatus and complicated readoutcircuit.In this dissertation, reflective optical readout uncooled infrared imaging devices for8～14μm IR have been studied. The pixel structures comprise a micro mirror, which is usedto absorb IR radiations and reflect readout visible light, two bi-material beams, which aresensitive to heat, two thermal isolation beams, which can prevent the leakage of heat, andtwo anchors, which can support the whole pixel.Firstly, the theories of designing pixel structure have been introduced. Aiming at bendof micro mirror, which is cause by bi-metal effect, two kinds of pixels have been proposed.One is with the micro mirror locating on extended direction of bi-material beam, named"a", the other is with the micro mirror locating on back inflected of bi-material beamdirection, named "b". The influences of beams length, beams length ratio and workpressure on all performances have been taken into account harmoniously to design andoptimize the dimension and work pressure of the pixels. The thermal-mechanicalsensitivity of these designed pixels can reach 10³ rad/K magnitude, and NETD_device can getmK magnitude.The effects of temperature compensate beam have been proved by ANSYSsimulation.A novel pixel with BMB-MM (bi-material beam-micro mirror integrative) structurehas been proposed. The BMB-MM structure can absorb IR, produce thermal-mechanicalsignal and reflect readout visible light. This kind pixel has been designed and optimized by analyzing the influence of area of BMB-MM, aspect ration of BMB-MM and workpressure on all those performances. The BMB-MM pixel has not only performancescomparative a, b pixel, but also larger fill factor.The fabrication progress flow has been designed with XeF₂ etching Silicon to releasestructure as cut-in point. Some key fabrication technologies have been studied, such asanchor protection, stress balance of the two materials, the compatibility of XeF₂ and DRIE.And the influences of some progresses on mirror roughness have been analyzed.A flat form was set up to test some performances of those pixels. The test resultverified the correlative theory analysis in allowable error range.