基于微机械的光调制热成像器件研究

【作者】 张流强；

【导师】 杨根庆；

【作者基本信息】 中国科学院上海冶金研究所 ， 微电子学与固体电子学， 2000， 博士

【摘要】 红外侦察和检测是一种有着广泛应用的关键技术，但红外相机的高昂价格 限制了它们的应用范围。为了实现廉价而高性能的红外探测器，新技术开发方 兴未艾，而采用光学读出方式的微机械红外成像阵列是最有竞争力的侯选者。 论文设计并制作了一种新颖的、可用于制造全光型热像仪的微机械热成像器件 （LMTID）。该器件具有灵敏度高、填充率大，响应时间短、显示亮度高，体积 小、能耗低等优点。 论文首先创造性地提出了光调制热成像器件的两种设计，并分别进行了 理论计算和有限元模拟。 这里首先建立了LMTID的悬臂梁模型，并采用悬臂梁理论分析了器件的 灵敏度、最小可探测能量及响应时间，并对双材料层的厚度比进行了优化设计。 采用ANSYS 5．4程序进行的有限元静态分析给出了LMTID的灵敏度，动态分 析则给出了器件的热响应时间。三层结构的LMTID的灵敏度可达0．03m／W，响 应时间约6ms。两层结构的LMTID的灵敏度可达0．00895m／W，响应时间为 3．6ms。这些结果表明光调制红外成像器件可以实现优于传统红外传感器或成像 仪的性能。 LMTID的制备是一个技术挑战，这部分内容包括微机械加工和芯片封 装两个方面。 微机械加工方面，首先采用多晶硅表面微机械技术制备了基于Al/Poly-Si 的LMTID芯片，制备中主要解决了残余应力消除和湿法释放所带来的表面张力 问题，采用超临界CO₂干燥技术成功地实现了LMTID的干燥并最终制备出具有 悬空微结构的LMTID芯片样品。 在多晶硅表面微机械技术的基础上，独立地提出了一种新的微机械表面加 工技术──硅牺牲层表面微机械技术，该技术具有加工步骤少、表面自动保持 平整、牺牲层厚度可在很大范围内调节等优点，特别适合LMTID的制备。采用 硅牺牲层表面微机械技术成功试制了一批基于Al／SiO₂双材料组合的LMTID样 品，这些样品的微结构具有高度的均匀性，表明该工艺不仅能够确保演示性样 中国科学院博士学位论文 摘要 品的制备，而且可适用于大阵列器件的生产。 无须引线使得LMTID的封装大大简化，论文提出了一种采用黄铜金属外 壳进行封装的技术，并成功获得了封装样品。 LMTID相关的光学设计与实现是LMTID高性能的保证，也是论文的一 个重要部分，此部分探讨了干涉光调制系统与红外成像系统的原理与理论设 计。干涉光调制系统包括迈克尔逊干涉型光调制系统、法－拍干涉型光调制系 统及Veeco表面轮廓仪干涉测量系统。 迈克尔逊干涉型光调制系统的理想光调制曲线是一条余弦曲线，但光谱线 结构对光调制结果有重大影响。在双谱线情况下，调制比随光程差呈周期为 V丛的周期性变化。在有一定宽度的谱线情况下，调制比随光程差的增加而衰 减，因而存在一个最大光程差人‘／Al。为此，迈克尔逊干涉型光调制系统应当工 作在0光程差附近以实现低噪声及高增益。 法－琅干涉型光调制系统是一种多光束于涉测量系统，具有陡峭的调制峰。 理论分析发现，为了实现高灵敏度的干涉测量，要求下反射面（LMTID）具有 尽可能高的反射率，且上反射面的反射率要与之相接近。 Veeco表面轮廓仪系统是一种干涉显微测量系统。它可用相位漂移干涉测 量模式（PSI）测量小位移，而用垂直扫描干涉测量模式（VSI）来测量大的位 移。 ．最后，论文叙述了LMTID样品的红外传感与成像的试验，并对结果进 行了分析讨论。 为实现红外传感与成像试验，设计了两种基于Veeco表面轮廓仪测试方式， 并加工了相应的试验装置。样品表面微结构的初始状况分析表明LMTID的微镜 阵列具有很高的均匀性，可以满足干涉成像的要求，并具备了制作大规模阵列 的潜力。微镜的初始变形在0．2～0．4pm范围，通过应力消除措施可进一步降低 到 0＊卜m以下。红外响应的测试结果定性地证明了 LMTID进行红外成像的能 力，采取改进措施后可进一步定量测量LMTID的红外响应曲线。更多还原

【Abstract】 Infrared (IR) reconnaissance and detection is a key technology with a wide spectrum of application; however, high price of JR cameras has limited the application to a few selected areas. To achieve inexpensive JR detectors with high performance, many efforts have been involved in the exploration of new technologies, among which micromachined IR imaging arrays with optical readout systems are the most promising candidates. A kind of novel micromachined thermal imaging device, light modulating thermal image device (LMTID), that can be employed in all-light-processing thermal imagers is presented in this thesis, having advantages such as high sensitivity, high fill factor, short response time, high display brightness, small volume, and low power consumption. ?Two kind of design on light modulating thermal image device are posed originally in this thesis, and theoretical calculation and finite element simulation are performed for them. Cantilever models are suggested for the two kind of LMTID, then the sensitivity, the minimum detectable power and the response time of LMTID are estimated with simplified beam theory, and the thickness ratio of bimaterial beams are optimized. Static finite element analysis with ANSYS 5.4 program gives the sensitivity of LMTID, while dynamic analysis gives the thermal response time. Three-layer-structured LMTID can achieve a sensitivity of O.O3mIW and a response time of 6ms, while two-layer-structured LMTID can achieve sensitivity up to O.OO895m1W and corresponding response time of 3.6ms. These results demonstrate the potential high performance of LMTID compared with conventional JR detectors. ?The fabrication of LMTJD is a technological challenge, which includes two parts of contents, micromachining process and chip package. On micromachining side, LMTID chips based on AlfPoly-Si material combination were firstly fabricated using poly-Silicon a micromachining technology, in which primary issues of residual stress and capillary effect coming from wet release were addressed. Super critical CO2 drying technology was applied to the drying of the devices ?iii ? 4~眫ti~ successfully. On the base of poly-silicon micromachining technology, a kind of novel surface micromachining technology, silicon-sacrificial-layer surface micromaching, is presented in this thesis. With advantages of less process steps, surface auto flatting, and sacrificial layer thickness adjustable over rather a wide range, silicon-sacrificial-layer surface micromaching technology is favorable for the fabrication of LMTID. LMTID samples based on Al/S i02 material combination were made successfully using silicon-sacrificial-layer surface micromaching technology, which have shown great uniformity in their microstmctures. It is demonstrated that this micromachining technology can ensure not only the fabrication of functional samples, but also the production of future large format devices. The package of LMTID benefits a lot from the wirelessness of LMTID. Package with brass shell is applied to test samples successfully. ?Optical design and realization concerned with LMTID is更多还原