【作者】 崔梦；

【导师】 胡明；

【作者基本信息】 天津大学 ， 微电子学与固体电子学， 2004， 硕士

【摘要】 自1990年以来,多孔硅材料一直以其出色的发光性能受到研究者的重视。近几年来,随着微电子机械系统(MEMS)的发展,多孔硅优良的机械性能和热学性能逐渐为人们所关注,成为MEMS中新兴的牺牲层材料和绝热层材料。本文主要针对多孔硅材料的基本性质及其在MEMS中作为绝热层的应用进行了研究。采用双槽电化学腐蚀法制备多孔硅,通过原子力显微镜分析其表面形貌发现制备的多孔硅孔洞分布均匀,孔径尺寸在15~50nm范围内。同时研究了腐蚀时间和电流密度对多孔硅深度及其孔隙率的影响,发现电化学腐蚀法制备多孔硅的腐蚀速率在腐蚀前期阶段基本是一定值,但到腐蚀后期阶段随着孔深的增加腐蚀速率有所下降。同时发现对于不同的腐蚀电流密度,多孔硅的孔隙率都有随腐蚀时间的延长先增加后降低的趋势。为了适应在大尺寸硅片上制备多孔硅的要求,对原电池法制备多孔硅进行了初步研究,主要研究了背电极的制备条件对多孔硅性能的影响,发现增加背电极的厚度对改善多孔硅的均匀性及减小其孔径尺寸有一定的作用。针对多孔硅在制备后易发生龟裂的现象,用微拉曼光谱法分析了多孔硅的残余应力,结果表明随多孔硅孔隙率的上升其内部残余应力有增加的趋势。同样采用微拉曼光谱法对多孔硅的热导率进行了成功的测量,结果表明,多孔硅的热导率随其孔隙率和厚度的增大而明显下降,实验中热导率最低可达到0.624W/mK。为对比多孔硅层与硅衬底二者间绝热效果的差别,将氧化钒热敏电阻分别沉积在多孔硅绝热层与硅衬底上,发现多孔硅良好的热绝缘性能使得在其上面制备的氧化钒热敏电阻的灵敏度远高于在硅上制备的热敏电阻,且热敏电阻的灵敏度随多孔硅孔隙率和厚度的增大而升高。更多还原

【Abstract】 Since1990, the photoluminescence of porous silicon (PS) was always the focus of attention. But with the development of Micro-Electro-Mechanical System (MEMS) technology, porous silicon has become a new kind of sacrificial and thermal insulating material used in MEMS due to its excellent mechanical and thermal isolation properties. The basic characters of PS and the application of PS as thermal isolation layer in MEMS are studied in this paper. Double-cell electrochemical etching was used to prepare PS. Through analysis the morphological characters of PS by AFM, it is found that the PS is uniform and the hole diameter is in the range of 15~50nm. The thickness and porosity of PS, which are affected by the etching time and etching current density, are discussed briefly. The result shows that the etching speed of PS is constant at the early stage, but at the later stage, the speed becomes slow with the increased depth of the hole. It is also found that the porosity values of PS samples prepared by different current density have the same trend that the porosity increasse firstly and then decreases with the etching time. In order to meet the requisition of preparing PS on large size silicon chip, pilot study is performed on preparing PS by galvanic element method. It is found that the uniformity of PS can be improved and the pole scale can be decreased by increasing the thickness of Pt film electrode. To study the crack phenomenon of PS, micro-Raman spectroscopy (MRS) is used to measure the residual stress of PS. The result shows that the tensile stresses increase with porosity of PS. The thermal conductivity (TC) of PS is also measured successfully by MRS. It is found that the TC of PS decrease rapidly with increasing porosity and thickness, and the lowest TC value of PS we prepared is 0.624W/mK. To contrast the thermal isolation efficiency between PS and silicon, VxOy thermal sensitive resistances are deposited respectively on the PS layer and the silicon substrate. It is found that the sensitivity of resistance deposited on PS layer is better than the resistance deposited on silicon substrate. And the resistance’s sensitive is improved with the increasing porosity and thickness of PS.更多还原