【作者】 吕宇强；

【导师】 胡明；

【作者基本信息】 天津大学 ， 微电子学与固体电子学， 2007， 博士

【摘要】 红外探测器发展的方向是非制冷、低成本以及小型化。基于热敏电阻的测辐射热计式红外探测器是主流的低成本非制冷红外热探测器之一,近年来越来越受到各国研究者的关注。对其的研究集中在两个方面:一是不断提高探测材料性能;再一个是探测器热绝缘结构方面的研究和改进以获得高响应的探测器。具有优异热敏性能的氧化钒薄膜材料是非制冷测辐射热计红外探测器的首选的热敏电阻材料。制备合适的薄膜电阻值且具有大的电阻温度系数（TCR）的氧化钒薄膜是实现高探测率红外测辐射热计的基础。本文利用新颖的对靶反应磁控溅射工艺制备了氧化钒薄膜材料,运用正交实验进行了工艺参数的研究,通过选择不同的工艺参数和不同的参数水平,得到了氩氧比例、溅射功率、工作气压、基片温度、基片类型以及真空退火等条件对氧化钒薄膜性能的影响,确定了最佳工艺参数。对得到的氧化钒薄膜的组成、结构和性能进行了测试分析。扫描电子显微镜（SEM）原子力显微镜（AFM）形貌分析表明薄膜具有均匀致密的表面,X射线光电子能谱分析（XPS）确定了其成分组成主要为V₂O₅、VO₂和少量的V₂O₃;对氧化钒薄膜电阻温度特性的研究表明,薄膜成分中各价态钒离子的比例对TCR和室温电阻有着重要的影响。钒的总体价态越高,室温电阻越大,TCR也越大;TCR较高并且阻值适当的样品中,钒的总体价态接近+4价。在常用作微测辐射热计MEMS结构层材料的氮化硅基底上沉积氧化钒薄膜所确定的最佳工艺条件为工作气压:2.0 Pa,氩氧流速比:Ar:O2 =48:0.5,基片温度:200℃,溅射功率: 210W。该工艺条件下薄膜材料在室温附近具有合适的薄膜电阻（14KΩ/□左右）以及高的温度电阻系数（-3.17%/℃）,所研制得到的氧化钒薄膜工艺重复性好,可以和半导体工艺兼容,非常适合于非致冷红外测辐射热计探测器应用。多孔硅材料作为牺牲层材料或绝热层材料均可为探测器单元的绝热结构制作提供新思路和解决途径。对具有多孔硅热绝缘层的氧化硅基底以及直接在硅衬底的氧化硅基底上淀积的氧化钒薄膜热敏特性进行对比研究表明,采用多孔硅结构可达到很好的绝热效果。另外,研究表明采用双槽电化学法制备的多孔硅腐蚀速率高,腐蚀后获得具有与掩模相同的表面轮廓和平整的底面的凹槽,适于用作牺牲层材料。利用有限元方法指出微测辐射热计微桥结构的设计思路,热分布分析表明对角支撑的探测器单元具有最好的温度梯度均匀性。对微桥的一些关键尺寸参数在规定的取值空间内进行建模优化设计,并分析了这些参数对位移形变和应力的影响。更多还原

【Abstract】 The trends of infrared(IR) detector are being uncooled, cheaper and more convenient. Bolometer which is a dominant low-cost uncooled thermal infrared detector based on thermistor have attached more and more attention by researchers around the world. Emphases are focused on two aspects, one is to improve the property of thermistor material continually to obtain high detector performace; the other is the research and improvement on thermal isolation structure of detector.Vanadium oxide with outstanding thermal sensing property is an ideal thermistor material for bolometer application and the fabrication of vanadium oxide thin film with high temperature coefficient of resistance (TCR) and suitable film resistance is the base of high detectivity of microbolometer. In this paper, Vanadium oxide thin film with nanostructure was deposited by novel facing targets DC reactive sputtering technique using V metal as target and the effect of deposition parameters including ratio of Ar/O2, sputtering power, work pressure, substrate temperature, sustrate types and vacuum annealing on the performance of vanadium oxide thin films is analyzed by choosing different level of these parameters in the orthogonal experiment. Optimal deposition parameters were defined. X-ray photoelectron spectroscopy analysis revealed the vanadium oxygen state of the film, which included V2O5、VO2 and a few V2O3. Atomic force microscopy surface morphology indicated a planar and compact film surface. TCR becomes higher (lower) as the higher (lower) sheet resistance. In the VOx films with high TCR and moderate sheet resistance, the average valence of vanadium is about +4. The optimal deposition parameters of vanadium oxide film on Si3N4 substrate, which is a common MEMS structure material in microbolometer use, were defined as follow: Working pressure: 2.0 Pa, gas flow ratio: Ar:O2 =48:0.5, substrate temperature 200℃, sputtering power: 210W. The temperature coefficient of resistance (TCR) as-deposited was high up to -3.17%/℃and the sheet resistance was about 14KΩ/□around room temperature. This deposition process has nice repetitivity and can be compatible with semiconductor process, which implied promising application in uncooled microbolometer infrared (IR) detectors.porous silicon,used as sacrificial layers or thermal insulator in the multi-layer structure can provide new methods to the fabrication of thermal isolation structure, the contrast result of the thermal sensing property of VOx resistance under a small power input deposited on porous silicon substrate and silicon substrate revealed good thermal isolation property of porous silicon layer. Otherwish, Porous silicon prepared by double-cell electrochemical etching has a high removing speed and it is found a trench was formed with almost the same pattern with the mask and flat bottom after etching, which implicit it is suitable for sacrificial material application.The finite element method was used in the design of microbridge structure for mcirobolometer, the temperature distributing analysis indicate the best uniformity in the structure supporting on diagonally position. Optimizing analysis of the Key scale parameters of microbridge was carried out in the seting scale space using a finite element model, the effect of these parameters on deformation was analysed.更多还原