MEMS系统级设计与基于多端口组件网络的建模方法

MEMS的系统级设计对保证其整体综合性能和合理开发MEMS产品至关重要。针对MEMS的多能量域耦合、多信号混合的特点以及能量非保守等特殊要求 ,提出了基于多端口组件网络的MEMS系统级建模方法———采用多端口组件表示MEMS的功能结构部件 ,组件与组件通过端口联成网络表示整个系统 ;用统一规范化的微分代数方程表征并用硬件描述语言表述多端口组件。针对梁等具体的MEMS功能结构部件 ,采用宏建模方法确定其行为方程 ,从而得到有特定物理意义的、可供重用的组件模型。最后 ,给出了微加速度计的基于多端口组件网络方法的系统级设计示例     

Generation of component level fault models for MEMS

Component level (nodal) simulations have been proposed to both implement closed loop simulation of complete microsystems to support the migration to shorter design cycles and implement fault models of micromechanical components. Within such a simulation environment, library cells in the form of behavioural models are used for the basic components of microelectromechanical (MEM) transducers, such as beams, plates, comb-drives and membranes. This paper presents both methodologies to generate the model parameters required for the implementation of accurate component fault models and simulation results from representative defective structures in a MEMS product.     

多层梁机电耦合系统的等效电路宏模型

实现MEMS器件系统级模拟的关键是建立其宏模型。由单层梁构成的机电耦合系统的等效电路宏模型 ,已做过深入的研究 ,但实际的MEMS器件通常都是多层的 .本文提出了一种基于力 电压 (F V)类比的、适用于由多层梁构成的机电耦合系统的等效电路宏模型 ,该模型可进行小信号时域和频域分析 ,能为多层梁机电耦合系统的设计带来很大的方便。模拟结果表明 ,该模型具有较高的精度     

The nonlinear dynamic response of microbeam of MEMS capacitive switch under mechanical shock

The microelectromechanical system (MEMS) capacitive switch based on clamped?Cclamped microbeam has garnered significant attention due to their geometric simplicity and broad applicability, and the accurate model which describes the multiphysical effects of MEMS capacitive switch should be developed to predict the nonlinear dynamic response of clamped?Cclamped microbeam. A improved macromodel of the clamped?Cclamped microbeam-based MEMS capacitive switch is presented to investigate the nonlinear dynamic response of clamped?Cclamped microbeam of MEMS capacitive switch under different mechanical shock in this article, the macromodel provides an effective and accurate design tool for this class of MEMS devices because of taking account into some effects simultaneously including midplane stretching effect, residual stress and different mechanical shock loads. A numerical analytical method based on multimode Galerkin discretization is presented to investigate the nonlinear response of clamped?Cclamped microbeam of MEMS capacitive switch under the different mechanical shock loads. The results show that using five or more modes can be sufficient to capture the nonlinear dynamic response of clamped?Cclamped microbeam, and the microbeam experiences a mechanical shock load as a quasi-static load or a dynamic load depending on the ration between the natural periods of the structure and the period or frequency of mechanical shock load. The proposed method gives the identical results to other numerical methods in the literature. Moreover, this method is straightforward to implement and could save computation efforts while not losing accuracy.     

基于部件库的MEMS设计方法

针对当前MEMS设计工具中机械性能评测不充分的问题 ,提出了基于部件库的MEMS设计方法 ;介绍了部件及部件库的概念和基于部件库的MEMS设计环境的总体结构及关键技术。完成了各关键技术的攻关 ,并建立了一个原形系统。     

Deformation analysis in microstructures and micro-devices

The mechanical behaviors of microstructures and micro-devices have drawn the attention from researchers on materials and mechanics in recent years. To understand the rule of these behaviors, the deformation measurement techniques with micro/nanometer sensitivity and spatial resolution are required. In this paper, a micro-marker identification method is developed to measure microstructure deformation. The micro-markers were directly produced on the top surface of microstructures by taking advantage of ion milling of focused ion beam (FIB) system. Based on the analysis of marker images captured by electronic microscope with specific correlation software, the deformation information in microstructures can be easily obtained. The principle of the technique is introduced in detail in the paper. An example experiment was executed to measure the displacement and strain distribution in a MEMS device. Obtained results show that the technique can be well applied to the deformation measurement of the micro/nano-electro-mechanical-systems (MEMS/NEMS).     

MEMS微波功率传感器的悬臂梁弯曲模型研究北大核心

为了研究电容式MEMS微波功率传感器悬臂梁的非线性运动，建立了MEMS悬臂梁在空间域上的弯曲特性模型，综合考虑静电力、轴向应力以及残余应力对悬臂梁非线性运动的影响，求解得到动力学微分方程。在此基础上研究在不同杨氏模量、驱动电压和残余应力下悬臂梁的弯曲特性，解析得到对应的悬臂梁弯曲特性曲线与轴向应力曲线。使用有限元分析软件ANSYS对不同驱动电压下的悬臂梁下拉位移进行仿真，并对仿真结果与解析结果进行比较。结果表明，在驱动电压从10 V到20 V的变化过程中，仿真结果与模型解析结果具有一致的趋势，两者间的最大误差仅有8.81%。对电容式MEMS微波功率传感器的悬臂梁弯曲特性的研究具有一定的参考价值和指导意义。     

GaAs基高性能MEMS微波功率检测芯片

为了提高电容式MEMS微波功率检测芯片的性能,设计了一种GaAs基高性能MEMS微波功率传感芯片。通过建立双导固支梁电容模型,分析了传感芯片的传输特性、过载功率与灵敏度特性。在双导固支梁电容模型中提出了平行极板的两个等效条件;同时提出了一种新的梁宽等效方式,解决了双梁结构等效梁宽的失配问题,减小了模型的相对误差。双导固支梁电容模型很好地解释了导向梁的厚长比与初始高度对传感器过载功率和灵敏度的影响。测试结果表明,双导固支梁MEMS微波功率传感芯片在200 mW输入功率内的灵敏度为14.3 fF/W,而灵敏度的理论值为13.5 fF/W,两者的相对误差仅5.6%。因此,该理论模型对固支梁MEMS微波功率传感芯片的设计具有一定的借鉴意义。     

MEMS虚拟组装设计的建模研究

虚拟组装是基于部件库的MEMS设计系统的重要组成部分 ,虚拟组装研究的重点在于建立组装模型 ,以表达部件之间的组装关系和进行组装顺序的规划。本文结合MEMS的层次性特点 ,提出了增强关联图的组装模型 ,并在组装关系纵横分类基础上 ,提出增强关联图的简化算法 ,最终采用拆卸法完成组装顺序的规划。     

固支梁微传感器等效电路宏模型及IP库的建立

针对 MEMS器件中的固支梁结构 ,采用了 SPICE中标准多项式受控源的形式和模态分析的方法 ,运用 F-I类比的电路形式建立了固支梁微传感器的多模态小信号等效电路宏模型 ,并建立了相应的 IP模型库单元。在外加力作用下 ,用 SPICE软件调用固支梁的 IP库并结合外加电路进行了系统级的模拟 ,得到微传感器分布参数的电学参量输出特性曲线 ;最后采用 COVENTORWARE软件进行了模型的各个模态的谐振频率和相关曲线的验证     

MEMS微传感器件IP库的建立方法

为实现MEMS器件系统级的模拟,运用等效电路宏模型的方法建立相应的IP模型库单元。本文以悬臂梁结构的微传感器为例,描述了如何根据基本结构与数学方程建立等效电路宏模型,并采用COVENTORWARE软件进行了模型的各个模态的谐振频率和相关曲线的验证,最后通过我们自行开发的IP库单元建立接口软件对单元进行了封装与入库。     

Reliability of MEMS shallow arches based actuator under the combined effect of mechanical shock and electric loads

Critical issues for the development of MEMS devices are their performance, reliability and survivability when subjected to unwanted loads, such as when dropped on a hard surface. These active forces can lead to tremendous destruction in these tiny mechanisms, such as stiction and all related short circuit problems in MEMS devices. Investigating the reliability of micro-structures under mechanical shock loads is a challenging job, driven, in part, by the large deflections that exacerbate system nonlinearities, such as those due to geometric (such as mid-plane stretching) and also the actuating nonlinear electric load. The proposed work aims to establish computationally efficient approaches that are capable of analyzing the transient dynamics of bi-stable MEMS devices, such as shallow arches, to mechanical shock and electric loadings. This investigation aims to improve the understanding of how mechanical shock loads can deteriorate the bi-stability of MEMS shallow arches. To this end, a Galerkin expansion reduced-order modeling (ROM) will be exploited. The capability of the ROM in simulating the bi-stable dynamical response of such devices to the combined effect of electrostatic force and shock load is thoroughly studied and analyzed. The ROM is utilized to explore the effect of several design parameters on the dynamic response of initially curved microbeams to shock loads: such as the shock amplitude, the shock duration, the beam initial curvature, and the DC voltage. Universal curves for the snap-through and pull-in voltages thresholds versus shock amplitude for various values of the nondimensional design constraints of the ROM are generated. These curves will present valuable information about the interaction between the shock and electrostatic forces and how to utilize this interaction to build new devices and propose new technologies.     

微机械虚拟运行的实现框架

简要论述了虚拟运行在MEMS设计系统[1,2 ] 中的重要性 ,引入了动态运动规律和数学库的概念 ,提出了在单机多任务系统上 ,以事件发生时间推进的机制 ,带有多个运动部件及其运动规律的微机械系统虚拟运行实现框架。并结合静电微马达和双金属驱动微流量泵为例 ,分析了虚拟运行中数学库的组织 ,动态运动规律的产生过程以及三维可视化的实时问题 ,所提出并采用的实现框架适用于微马达[3] 、微泵[4 ] 、微加速度计[5] 等微电子机械系统的设计和虚拟运行     

Study of intermodulation in RF MEMS variable capacitors

This paper provides a rigorous study of the causes and physical origins of intermodulation distortion (IMD) in RF microelectromechanical systems (MEMS) capacitors, its analytical dependence on the MEMS device design parameters, and its effects in RF systems. It is shown that not only third-order products exist, but also fifth order and higher. The high-order terms are mainly originated by the nonlinear membrane displacement versus applied voltage and, in the case considered in this study, with an additional contribution from the nonlinear dependence of the reflection coefficient phase on the displacement. It is also shown that the displacement nonlinear behavior also contributes to the total mean position of the membrane. In order to study these effects in depth, an analytical frequency-dependent IMD model for RF MEMS based on a mobile membrane is proposed and particularized to the case of a MEMS varactor-a device for which IMD can be significant. The model is validated, up to the fifth order, theoretically (using harmonic balance) and empirically (the IMD of a MEMS varactor is measured). To this end, a two-tone IMD reflection measurement system for MEMS is proposed.     

缩短RFMEMS开关释放时间的上悬梁方法

针对RF MEMS开关释放时间过长的问题,提出了在开关梁上设计一个上悬梁的方法,以增大开关梁所受压膜阻尼,抑制开关梁在平衡位置附近的振动,从而缩短RF MEMS开关的释放时间。给出了这种方法的相关理论、等效模型及仿真结果。通过ANSYS仿真雷声梁在设置上悬梁前后的动态特性:对于4μm高的梁,释放时间由设置上悬梁前的103μs(0.5μm厚),176μs(0.8μm厚)和232.5μs(1.1μm厚)分别下降为53.3,89和123.4μs;对于3μm高0.5μm厚的梁,释放时间由43.3μs下降为22μs。仿真结果均表明:在标准大气压下,当雷声梁高度为上悬梁高度的一半时,加入上悬梁后雷声梁的释放时间约为原来的1/2,即开关速度约为原来的2倍。     

芯片粘接工艺对MEMS性能影响的单元库法模型

芯片粘接工艺引起的器件-封装热失配会对MEMS器件的可靠性和性能产生显著影响.常用FEM模拟在分析此类问题时比较费时且缺乏明确的理论意义.文中基于单元库法思路提出了该类问题的理论建模方法,并依此举例分析了芯片粘接工艺中各可变参数对双端固支梁pull-in电压的影响,其结论与Ansys模拟结果一致.该方法简单准确,对MEMS的封装-器件协同设计将有着实际的意义.     

压电双晶梁MEMS传感器的稳健设计研究

微机电系统(MEMS)传感器结构参数的微小变差会影响其性能稳定。为提高MEMS传感器性能的稳健性,以压电双晶梁MEMS传感器为例,根据Smits模型,分析压电双晶梁的设计变量和噪声因素的随机性,建立基于随机模型的稳健设计数学模型;编制算法程序,确定MEMS传感器的最优设计解结果优于原设计方案。对比其稳健设计容差模型所得优化解,两者误差率为6.17%,验证了稳健设计结果的正确性。研究表明,即使设计变量存在变差,稳健设计仍能提高MEMS传感器的性能,并保证设计解的稳健性。     

傍轴光束薄透镜传输的统计行为

在光流体模型(HMO)的理论基础上,引用等效高斯光束方法,研究了傍轴光束的薄透镜传输的统计行为,给出了像差的处理方法并讨论了像差对光束质量因子的影响。     

波束波导馈电的新型偏置近场卡塞格伦天线

提出一种新型偏置近场卡塞格伦天线,天线的主副镜均由具有圆口径的抛物面镜构成,给出了主副镜的几何参数和设计方程。采用非传统且适应高功率应用的波束波导进行馈电,天线系统（含波束波导）采用了几何光学和去极化的设计方法。根据照射锥削角和高斯束腰设计了方向图圆周对称的波纹喇叭馈源。在此馈源喇叭的基础上,根据高斯波束法得到波束波导各镜面尺寸。采用物理绕射理论对一个设计实例的方向图进行分析,证明该天线系统具有极低的交叉极化电平和旁瓣电平。     

超声跟踪铌酸锂反常声光器件的优化设计

给出了一种新的超声跟踪铌酸锂反常声光器件的优化设计方法,利用该方法系统计算了在不同入射角以及不同换能器片数情况下器件设计参数的准确数值。计算结果表明,该设计方法可以实现反常声光器件的超声跟踪,并且能够使器件获得更大的3 dB带宽和更高的衍射效率。