三维集成技术可以解决MEMS传感器与CMOS的工艺不兼容问题，增加MEMS传感器在材料选取时的自由度，提供异质集成能力，实现高互连密度，是目前微系统领域的研究热点之一。本文开发一种基于SOI单晶硅转移的三维集成技术，可以实现单晶MEMS传感器与CMOS的三维集成。并基于此技术，提出了一种新型的非制冷红外传感器结构。基于SOI单晶硅转移的三维集成技术的具体实施方法是：先在SOI硅片上制作MEMS传感器、在普通硅片上制作CMOS电路；然后将SOI翻转后通过一层中间键合层与CMOS电路进行键合，并去除SOI的硅衬底，实现将MEMS传感器层转移到CMOS电路的上方；制作垂直互连柱，实现上层MEMS传感器与下层CMOS的电连接；最后释放键合层，实现MEMS传感器的悬空。本文对上述三维集成技术中的关键工艺进行了研究。采用BCB作为中间键合层，通过优化键合参数，获得了无空洞的BCB键合界面。开发了两种提高BCB键合对准精度的方法，可以将BCB键合的键合后对准偏差减小到3μm以下。对硅衬底去除工艺进行了研究，实现了介质层薄膜的良好转移。通过优化刻蚀气体、功率、压强等参数，获得了优化的BCB垂直刻蚀和横向释放的参数。通过实验，本文验证了这套三维集成技术的可行性。基于该三维集成技术，提出了一种新型非制冷红外传感器结构。它利用悬空于CMOS电路上方的SOI单晶二极管作为传感器的敏感元件，具有噪声低、一致性好、易于大规模生产的优点。本文对红外传感器的吸收层、热隔离结构及二极管的参数进行了优化，完成160×120传感器阵列芯片的设计与制作。针对该红外传感器阵列，设计了CMOS读出电路，包括选取和激励电路、前端放大器、模数转换器及数据输出控制，并采用CSMC 0.35μm工艺制作完成。在分别完成传感器芯片与CMOS芯片的制作以后，成功实现了传感器与CMOS的三维集成。将单晶二极管红外传感器阵列悬空于CMOS电路的上方。对集成后的芯片进行了测试。结果表明，三维电连接良好，传感器电特性和温度特性正常，并表现出良好的一致性。
Three-dimensional (3-D) integration is a promising technology to overcome the material and process incompatibilities of MEMS sensors and CMOS. 3-D integration technology offers the possibility for heterogeneous integration of chips with different technologies, more freedom in materials and process during MEMS fabrication, and ultra high integration density between MEMS and CMOS. In this dissertation, a 3-D integration technology which is based on transferring the single crystalline of SOI on top of CMOS has been studied. The technology can realize the 3-D integration of single crystalline MEMS sensors with CMOS. Also, a novel uncooled infrared detector based on the 3-D integration technology has been proposed. The 3-D integration technology is based on transferring the single crystalline of SOI on top of CMOS. Firstly, the MEMS sensors are fabricated in the device layer of SOI wafer and the CMOS circuit is fabricated in normal silicon wafer. Then the SOI wafer is flipped and bonded with CMOS wafer using a polymer adhesive layer as bonding interface material. After bonding, the substrate of the SOI wafer is removed and the device layer of SOI is transferred on top of CMOS wafer. Conductive vias are fabricated to provide electrical interconnect between MEMS sensors and CMOS. Finally, the bonding interface layer is etched away to suspend free-standing MEMS structures.Several key process modules used in the above mentioned 3-D integration technology are studied. BCB is chosen as bonding interface material. By optimizing bonding parameters, void-free bonding interface is obtained. Two methods are investigated to improve the post-bonding alignment accuracy, which reduce the post-bonding misalignment to less than 3μm. The way to remove substrates of SOI wafers is studied and intact film transfer is achieved. By optimizing etching parameters such as etching gases, RF power, chamber pressure, the optimized parameters to achieve vertical and lateral etching of BCB is obtained. Through experiment, the feasibility of the above mentioned 3-D integration technology is verified.Based on the 3-D integration technology, a novel uncooled infrared detector structure is proposed. Single crystalline diodes suspending over the CMOS wafer is used as sensing element of the infrared detector, which provides many advantages including low noise, high uniformity and suitability for mass production. In this dissertation, the infrared absorption layers, thermal isolation structures and diode parameters are optimized. The 160×120 infrared sensor array is designed and fabricated. The CMOS circuit chip for the infrared sensor array is designed including addressing, electrical excitation, amplification and analog-to-digital conversion. The CMOS circuit chips are fabricated using CSMC 0.35 μm process.After the accomplishment of MEMS sensors and CMOS, the 3-D integration is conducted successfully. The single crystalline diode infrared sensor arrays are suspended on top of CMOS flatly. Electrical tests of the integrated chips are performed. The results show that the 3-D integration works well. The electrical and temperature characteristics of suspended sensors are well and show good uniformity.
