基于形变在线调控技术研究微热板气体传感器在应力作用下的稳定性和可靠性

Micro-hotplate gas sensor works at high temperature. Thermal stress and deflection of the multi-layer thin film will cause stability and reliability problem. In order to improve the stability and reliability of MHP gas sensors, we should understand the effect of stress on the stability and reliability of the sensors. In this project,a surface-micromachined micro gas sensor for methane detection is taken as the object of study. Several novel deflection online adjustable MHP gas sensor systes are designed based on the electrostatic actuators,and with these systems, the stress on the gas sensor can be adjusted on chip, and the effect of stress change on the properties of MHP gas sensor is studied experimentally; The micro creep discipline of the gas sensing film or on the interface between films under stress and high temperature are studied with molecular dynamics calculation; The measurement results combined with the results of computer modeling, the performance degredation and the failure principle of the MHP gas sensors are studied, and solutions for stability and reliability improvement of MHP gas sensors are discussed, so as to provide both experimental and theoritical supports to achieve stable and reliable MHP gas sensors. The research work of this project will not only push forward the application progress of MHP gas sensors, but also provide scientific and technologic reference for the studies of other MHP-based MEMS devices.

微热板气体传感器长期工作在高温状态，其多层复合膜的热应力和形变是影响器件稳定性与可靠性的重要因素。本项目面向提高硅微热板气体传感器稳定性和可靠性的重要需求，以掌握应力对微热板气体传感器的稳定性和可靠性的影响机制为目标，以表面加工型甲烷微热板气体传感器为研究对象，设计了几款新型的形变在线可调的微热板气体传感器片上系统，首次实现气体传感器应力的片上在线调节，进而通过实验手段研究和掌握应力对传感器的影响机制；并通过分子动力学仿真手段探索高温和应力作用下微结构的蠕变规律；实验与仿真相结合，掌握多种应力条件下微热板气体传感器的性能退化模式和失效机理，给出提高微热板气体传感器稳定性和可靠性的途径的合理化建议，为实现稳定和可靠的微热板气体传感器提供实验和理论支持。本项目的成功实施，不但可以推进微热板气体传感器的实用化进程，而且对其它基于微热板的MEMS器件的深入研究也具有科学意义和技术参考价值。

微热板气体传感器长期工作在高温状态，其多层复合膜的热应力和形变是影响器件稳定性与可靠性的重要因素。本项目面向提高硅微热板气体传感器稳定性和可靠性的重要需求，以掌握应力对微热板气体传感器的稳定性和可靠性的影响机制为目标，以微热板气体传感器为研究对象，设计了几款新型的形变在线可调的微热板气体传感器片上系统，实验和有限元仿真结合分析了其在线调节能力，得到调节量微小的结论，以及结构差异可以获得不同形变和应力的器件。因此项目组采用MEMS和CMOS工艺制造了多种微热板气体传感器，利用它们在结构参数上的差异，通过实验手段研究和掌握了形变、应力、温度对传感器的影响机制，并获得几个重要结论：温度和应力分布共同决定了微热板气体传感器的薄弱环节，它位于工作区与支撑臂的连接处，此处温度和应力值均较高；形变对微热板可靠性有显著影响，形变大的微热板极限工作温度显著降低。通过分子动力学仿真手段探索高温和应力作用下微结构的的蠕变和气敏性能，并获得几个重要结论：ZnO表面的氧缺陷增加了有效吸附点，提高了气体吸附几率；有缺陷的不同晶面，在应力作用下的抗蠕变能力有显著差异；应力的存在会显著增加ZnO表面的气体吸附率； 温度对表面气体吸附效果的影响与气体种类有很大关系，例如氧气在高温下吸附率显著下降，而水的吸附受温度的影响不大。实验与数值计算相结合，分析了微热板气体传感器的不稳定性和失效机制，给出兼顾器件低功耗、高可靠性和稳定性设计目标的微热板气体传感器的结构优化设计准则，为实现稳定和可靠的微热板气体传感器提供了实验和理论支持。