【作者】 范茂彦；

【导师】 姜胜林；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2009， 博士

【摘要】 铁电厚膜非制冷红外焦平面阵列是新一代红外热成像系统的关键部件。热释电红外焦平面阵列具有成本低、无需制冷和对红外波长无选择性等优点,被广泛应用于军事和民用领域。钛酸锶钡（BST）铁电厚膜因具有优越的介电和热释电效应以及能与半导体技术兼容等特点,成为非制冷红外焦平面阵列的优选材料,用其制备的介电量热型非制冷红外焦平面阵列具有独特的优点。本文研究了红外探测器的噪声,电压响应率和电流响应率与BST厚膜及结构参数间的关系,改进了非制冷微测辐射热计焦平面阵列制备工艺。主要内容如下:对热释电探测器建立的一到三维模型进行了探讨,分析硅微桥结构的传热物理模型及其理论计算方法,提出了具有“桌形”绝热框架支撑的微桥结构,用有限元分析证明其有较小的热导,能获得较高响应率。研究了微桥绝热结构的刻蚀工艺及多孔硅绝热层制备工艺,在厚度为240μm的硅基片上制备了腐蚀坑深度大于200μm,桥面为200μm×200μm的微桥结构,成功制作出16×16的微桥结构阵列。采用电化学法制备了多孔硅,通过HF溶液浓度、电流密度和反应时间来控制多孔硅的孔径、孔隙率和膜厚。观测了样品的微观形貌,分析了热导率。用乙酸盐溶胶-凝胶法制备了Mn掺杂BST凝胶。微波烧结制备了BST纳米粉体和厚膜,粉体粒径60nm、厚膜粒径200nm左右。介电性能ε_Γ＞1000,tanδ＜2%。研究了La-Mn-Al离子掺杂对厚膜微观结构、介电性能的影响。La、Mn、Al离子共掺杂能显著地抑制BaSrTiO₃的晶粒生长,厚膜结晶过程析出多晶微粒,提高了厚膜均匀性和致密性。讨论了不等价掺杂及掺杂量对介电性能的影响。采用改进的溶胶-凝胶法在Pt/Ti/SiO₂/Si基片上制备了Mn掺杂六层不同组份梯度BST厚膜,厚度约为5μm,研究了梯度BST厚膜的微观结构及其介电性能,介电常数峰值为920,损耗约为1.8×10^-2。以钛酸钡凝胶薄膜种子层为不同组分BST厚膜间的夹层,在LNO/Pt/Ti/SiO₂/Si复合底电极上制备了厚度约为20μm的BST介电增强型夹层厚膜。结果表明,650℃热处理后的夹层厚膜为单一钙钛矿相,750℃热处理后的夹层厚膜在温度25℃、频率1KHz下相对介电常数和损耗峰值分别为1200和3%,室温附近较宽范围介温变化率大于1.2%/℃;BST夹层厚膜无裂纹,表面平整。提出了通过硅通孔技术实现垂直互连,提高像元占空比,缩短了互连引线长度,降低了信号延迟。用单晶硅湿法刻蚀加工方法形成通孔,利用直写技术将耐高温Ag-Pd导体浆料填充通孔,实现红外焦平面阵列底电极与硅基片背面倒装焊凸点互连。更多还原

【Abstract】 Ferroelectric thick-film （FTF） uncooled infrared focal plane array （UIFPA） is a key part of new-generation thermal imaging system. Pyroelectric IFPA has advantages of low cost, no need of refrigeration, no requirement for infrared wavelength, etc, it has been used in military and civil field. BST FTF has predominant dielectric and pyroelectric effects and may be compatible with semi-conductor technology, so it has become excellent material of UIFPA. Dielectric calorimetry UIFPA use BST as UIFPA has particular advantages.This work has investigated the relation between the noise of the infrared detector, voltage response rate, current response rate and kinds of parameters of BST thick film and structure. The fabrication technology of uncooled infrared focal plane array was improved. The main contents are as follows:The one-dimension, two-dimension and three-dimension models, which were set up for pyroelectric detectors, were analyzed. A kind of micro-bridge structure was provided in this work with desk-type adiabatic frame support, and the analysis results by finite element method showed that the minor thermal conductivity and high responsivity can be obtained.The etching technology of micro-bridge thermal insulation structure and fabrication technology of porous silicon heat insulating layer are researched. The micro-bridge structure with etch-pit depth over 200μm and bridge surface about 200μm×200μm was prepared on a silicon substrate with depth of 240μm, and 16×16 micro-bridge structure array was successfully made. Porous silicon samples were prepared by electrochemical method. The aperture, porosity ratio and film thickness of porous silicon could be controlled by different concentrations of HF solution, current density and reaction time. Micro structure of porous silicon samples was observed and thermal conductivity was analyzed.The stoichiometric proportion and doping of film can be controlled exactly as the result of the preparation of film by sol-gel method. The particle with 60nm in diameter and the films with 200nm in thickness were prepared by microwave sintering technology. The dielectric temperature characteristicε_r was larger than 1000, and tanδwas less than 2%. The influence of La-Mn-Al co-doping on the micro-structure of BST thick film and dielectric properties was analyzed. The co-doping of La, Mn and Al could markedly inhibit the growth of BaSrTiO₃ grain, and polycrystalline particles were precipitated during crystallization of the thick film to enhance the uniformity and compactness of thick film. The influence of unequal-valence and doping amount on the leakage current, dielectric loss and dielectric property was discussed. The Mn-doped BST thick films with six different layers of composition gradients were fabricated in the Pt/Ti/SiO₂/Si silicon chip by improved sol-gel method. The thickness of the thick film was about 5μm. Then the micro structure and dielectric property of the gradient thick film is studied, with dielectric coefficient 920 and dielectric loss approximately 1.8×0^-2. Taking the BST thin film as the interlining between the thick films with different components, the BST dielectric-reinforced interlining thick films of around 20μm thickness were made in the composite LNO/Pt/Ti/SiO₂/Si bottom electrode. The XRD patterns showed that there was only perovskite phase in the interlining thick films through heating treatment at 650℃. The relative dielectric constantε_r and dielectric loss tanδof the interlining thick film by heating treatment at 750℃were approximately 1200 and 3% in the case of 25℃and 1 kHz, respectively. The dielectric-temperature change rate was over 1.2%/℃within a wide range near 25℃. The surface of BST interlining thick film was smooth and compact without any fracture.In this work, we put forward that vertical interconnection could be realized by making use of the technique of Through-Silicon-Via （TSV） to enhance the duty, shorten the interconnect metallic line and cut the signal delay time. A through-hole is formed by silicon wet etching method, and then is filled with high-temperature resisting Ag-Pd conductive paste through use of direct writing technology, so as to realize the interconnection between the bottom electrode of infrared focal plane array and flip chip bonding bump at the back side of silicon substrate.更多还原