Hilton Allan, Temple Dorota S
Electronics and Applied Physics Division, RTI International, Research Triangle Park, NC 27709, USA.
Sensors (Basel). 2016 Oct 31;16(11):1819. doi: 10.3390/s16111819.
The reach and impact of the Internet of Things will depend on the availability of low-cost, smart sensors-"low cost" for ubiquitous presence, and "smart" for connectivity and autonomy. By using wafer-level processes not only for the smart sensor fabrication and integration, but also for packaging, we can further greatly reduce the cost of sensor components and systems as well as further decrease their size and weight. This paper reviews the state-of-the-art in the wafer-level vacuum packaging technology of smart sensors. We describe the processes needed to create the wafer-scale vacuum microchambers, focusing on approaches that involve metal seals and that are compatible with the thermal budget of complementary metal-oxide semiconductor (CMOS) integrated circuits. We review choices of seal materials and structures that are available to a device designer, and present techniques used for the fabrication of metal seals on device and window wafers. We also analyze the deposition and activation of thin film getters needed to maintain vacuum in the ultra-small chambers, and the wafer-to-wafer bonding processes that form the hermetic seal. We discuss inherent trade-offs and challenges of each seal material set and the corresponding bonding processes. Finally, we identify areas for further research that could help broaden implementations of the wafer-level vacuum packaging technology.
物联网的覆盖范围和影响力将取决于低成本智能传感器的可用性——“低成本”以实现广泛存在，“智能”以实现连接和自主。通过不仅在智能传感器制造和集成中，而且在封装中使用晶圆级工艺，我们可以进一步大幅降低传感器组件和系统的成本，并进一步减小其尺寸和重量。本文综述了智能传感器晶圆级真空封装技术的现状。我们描述了创建晶圆级真空微腔所需的工艺，重点关注涉及金属密封且与互补金属氧化物半导体（CMOS）集成电路的热预算兼容的方法。我们综述了设备设计师可选用的密封材料和结构，并介绍了在器件晶圆和窗口晶圆上制造金属密封的技术。我们还分析了在超小腔室中维持真空所需的薄膜吸气剂的沉积和激活，以及形成气密密封的晶圆对晶圆键合工艺。我们讨论了每种密封材料组和相应键合工艺的固有权衡和挑战。最后，我们确定了有助于拓宽晶圆级真空封装技术应用的进一步研究领域。
