电容式RF MEMS开关介质中电荷积累机理及其消除方法的研究

Capacitive RF MEMS switches show great promise for use in wireless communication devices, but the successful application of these switches is hindered by reliability issues: charge accumulation in the dielectric layer can cause irreversible stiction of the switch.In spite of huge effort has been made from many research groups worldwide for more than a decade to develop robust RF MEMS switches, the approaches of controlling dielectric charging are still limited so far.In this project, our objectives are to increase the understanding of charge accumulation in the dielectric layer and to learn how to design innovative and robust Capacitive RF MEMS switches.We will investigate charge injection mechanisms for eliminating charge injection, to manipulate the relaxation processes for reducing relaxation time, to control the charge polarity for neutralizing the injected charges. The approaches to reduce or eliminate charge accumulation in this project can be described as follows: Doping dielectric layer with donor or acceptor type impurity for creating recombination centers to speed up relaxation process of trapped charge; Designing double-dielectric-layers with different thickness ratio to blance the negative and positive charges injected from the two electrodes by optimizing the thickness ratio; Designing repulsive electrostatic driven MEMS Switch instead of electrostatically actuated MEMS switch to avoid high electric field produced across the dielectric layer when actuation voltage is applied.The research in this project will help us to develop a novel and robust RF MEMS switch for upcoming military and commercial applications in wireless communication.

电容式RF MEMS开关介质层中电荷积累所造成的开关不可逆转的"粘连"失效是制约其大规模商业化的瓶颈。近年来，诸多学者一直致力于解决该失效问题，至今依然没有找到消除电荷积累的有效方法，甚至电荷积累的基本机制尚不清晰。本项目将以用于开关的不同介质层中电荷的生成、注入、陷定和弛豫机理作为理论攻关；研究介质掺杂种类、位置、浓度对电荷积累、微波损耗的影响，寻求最佳掺杂材料在介质中引入"复合快态"，实现被陷电荷的快速自释放；设计研制双层介质膜开关结构，在保持激励电压和介质膜总厚度不变的情况下，研究厚度比对与电荷注入相关的电场、势垒、有效质量等各参数的影响，寻求最优厚度比平衡从正负两电极注入的异种电荷；设计静电斥力驱动式开关结构，避免开关处于"down"态位置时介质中产生的高电场，消除电荷积累的根源，为实现用于我国军事和商业无线通信领域的高可靠长寿命RF MEMS开关奠定理论基础和技术支撑。

电容式 RF MEMS 开关介质层中电荷积累所造成的开关不可逆转的“粘连”失效是制约其大规模商业化的瓶颈。近年来，诸多学者一直致力于解决该失效问题，至今依然没 有找到消除电荷积累的有效方法，甚至电荷积累的基本机制尚不清晰。本项目研究了不同介质层中电荷的生成、注入、陷定和弛豫机理；研究了介质掺杂种类、位置、浓度对电荷积累的影响，寻求最佳掺杂材料在介质中引入“复合快态”，实现被陷电荷的快速自释放；设计了双层介质膜结构，在保持激励电压和介质膜总厚度不变的情况下，研究了厚度比对与电荷注入相关的电场、势垒、有效质量等各参数的影响；设计了静电斥力驱动式开关结构，避免开关处于“down”态位置时介质中产生的高电场，消除了电荷积累的根源。