空气阻尼和残余应力对平面悬空薄膜振动特性的影响研究

Planar, suspended films play an significantly important role in the applications of MEMS/NEMS, which are widely used in the fields of telecommunication, defense, mechanical engineering, biomedical engineering and so on. Air damping and residual stress can directly affect the vibrations and quality factors of suspended films, which will further have effect on the functionality and reliability of the device. Therefore, this project will apply microfabrication technologies, including thin film deposition, photolithography to fabricate suspedned SiC and SiN membranes on Si substrates. Also an accurately controllable and measurable vacuum system will be designed. The dynamic characterisitics and quality factors of SiC and SiN membranes with a large range of residual stress will thus be systemically investigated in different vacuums by using experimental methods of nanoindentation and microscopic laser Doppler vibrometer, numerical method of finite element analysis and theoretical method of Rayleigh-Ritz energy method. Thus, the influence of air damping and residual stress on resonant frequencies and quality factors of suspended films will be studies as well. The research results will obtain the accurate effects of air damping and residual stress on vibrations of suspened thin film structures, which will further optimize the design and performance of nano thin-film devices.

平面悬空薄膜在微/纳机电系统中具有极其重要的应用价值，广泛用于通讯、国防、机械、生物医学等众多领域。空气阻尼和残余应力会直接影响到悬空薄膜振动特性和品质因子，进而影响器件的功能性与可靠性。为此，本项目拟利用薄膜沉积、光刻掩膜、硅刻蚀等微加工技术制备硅基悬空SiC和SiN 自由薄膜器件，研制精确可控与可测量的真空测试装置，利用纳米压痕仪、显微式激光多普勒测振仪等多种先进实验测试仪器和Rayleigh-Ritz能量法、有限元分析等理论与数值方法，对具有不同残余应力的SiC和SiN悬空薄膜在不同真空度下的振动特性与品质因子进行系统研究；探究空气阻尼和残余应力对悬空薄膜共振频率和品质因子的影响。研究结果可准确获取空气阻尼和残余应力对悬空薄膜结构振动的影响关系，可进一步优化纳米薄膜器件的设计和性能。

平面悬空薄膜在微/纳机电系统中具有极其重要的应用价值，广泛用于通讯、国防、机械、生物医学等众多领域。空气阻尼和残余应力会直接影响到悬空薄膜振动特性和品质因子，进而影响器件的功能性与可靠性。为此，本项目做了如下研究：构建了微膜振动的流固耦合动力学模型；建立了相应的有限元仿真模型，对理论方法的有效性进行了验证；利用表面/体硅微加工技术制备了硅基悬空自由薄膜器件；研制了薄膜力学性能测试系统和微纳结构光学表征系统；创建和发展了基于激光多普勒测振仪和激光位移传感器的微纳米结构动态测试方法。在此基础上，项目对具有不同残余应力的悬空薄膜在不同真空度下的振动特性与品质因子进行了系统研究。研究表明：空气等流体主要以附加质量形式对悬空薄膜的共振频率和模态产生影响；微膜结构的能量主要以声辐射形式向周围流体环境耗散，其品质因子受周围流体介质密度等性能的影响。值得注意的是，我们的研究还发现，微膜声辐射相关的品质因子会随残余应力的增加而减小，并随应力的改变展现出膜和板的双重行为。项目的研究结果对于开发、设计和优化微膜器件具有重要价值。