Numerical simulation and analysis of electrically actuated microbeam-based MEMS capacitive switch

The MEMS capacitive switch based on fixed-fixed microbeam has garnered significant attention due to their geometric simplicity and broad applicability. The accurate model which describes the multiphysical coupled-field of MEMS capacitive switch should be developed to predict their electromechanical behaviors. The improved macromodel of the fixed-fixed microbeam-based MEMS capacitive switch is presented to investigate the behavior of electrically actuated MEMS capacitive switch in this paper, the macromodel provides an effective and accurate design tool for this class of MEMS devices because of taking account into some effects simultaneously including fringing field effect, midplane stretching effect, residual stress and multiphysical coupled-field effect. The numerical analysis of mechanical characterizations of electrically actuated microbeam-based MEMS capacitive switch are performed by the finite element Newmark method, and the performances of static and dynamic of MEMS capacitive switch are obtained. The numerical results show that, with only a few nodes used in the computation, the FEM-Newmark gives the identical results to other numerical methods, such as the shooting method and experiments. Moreover, the proposed model can offer proper and convenient approach for numerical calculations, and promote design of MEMS devices.     

Design and modeling of a continuously variable piezoelectric RF MEMS switch

A structure for a piezoelectrically actuated capacitive RF MEMS switch that is continuously variable between the ON state and the OFF state has been proposed. The device is based on variable capacitance using a cantilever fixed at both ends that is actuated using a lead zirconate titanate thin film. Because the device is contactless, the reliability issues common in contact-type RF MEMS switches can be avoided. A comprehensive mathematical model has been developed in order to study the performance of the device, and allow for design optimization. Electrical measurements on test structures have been compared with the performance predicted by the model, and the results used to design a prototype RF MEMS switch. The model and simulations indicate the proposed switch structure can provide an insertion loss better than 0.7 dB and an isolation of more than 10 dB between 6 and 14 GHz with an actuation voltage of 22.4 V. The state of the device is continuously variable between the ON state and the OFF state, with a tunable range of capacitance of more than 15\(\times \).     

A novel DMTL capacitive switch with electrostatic actuation MAM capacitors

A novel DMTL capacitive switch with electrostatic actuation metal–air–metal (MAM) capacitors is presented. The top board of MAM capacitors will be pulled down together with the switch bridge. It has higher isolation in down-state than DMTL capacitive switch and has lower insert loss and higher self-actuation RF power comparing with MEMS shunt capacitive switch. Two of the novel DMTL capacitive switches are designed for high isolation and high self-actuation RF power, respectively. The calculated result shows that both of the two novel switches have lower insert loss than the MEMS shunt capacitive switch. The self-actuation RF power of them are 4 and 2.4 times that of MEMS shunt capacitive switch, respectively, at the cost of ?6.23 and ?3.54?dB reduction in isolation (30?GHz).     

串联电容式RF MEMS开关设计与制造研究

介绍了一种串联电容式RF MEMS开关的设计与制造。所设计的串联电容式RF MEMS开关利用薄膜淀积中产生的内应力使MEMS桥膜向上发生翘曲,从而提高所设计的开关的隔离度,克服了串联电容式RF MEMS开关通常只有在1GHz以下才能获得较高隔离度的缺点。其工艺与并联电容式RF MEMS开关完全相同,解决了并联电容式RF MEMS开关不能应用于低频段(<10GHz)的问题。其插入损耗为-0.88dB@3GHz,在6GHz以上,插入损耗为-0.5dB;隔离度为-33.5dB@900MHz、-24dB@3GH和-20dB@5GHz,适合于3~5GHz频段的应用。     

Design and simulation of a thermally actuated MEMS switch for microwave circuits

The design, modeling, and optimization of a novel, thermally actuated CMOS‐MEMS switch are presented in this article. This series capacitive MEMS switch solves the substrate loss and down‐state capacitance degradation problems commonly plaguing MEMS switches. The switch uses finger structure for capacitive coupling. The vertical bending characteristic of bimorph cantilever beams under different temperatures is utilized to turn the switch on and off. A set of electrical, mechanical, and thermal models is established, and cross‐domain electro‐thermo‐mechanical simulations are performed to optimize the design parameters of the switch. The fabrication of the switch is completely CMOS‐process compatible. The design is fabricated using the AMI 0.6 μm CMOS process and a maskless reactive‐ion etching process. The measured results show the insertion loss and isolation are 1.67 and 33 dB, respectively, at 5.4 GHz, and 0.36 and 23 dB at 10 GHz. The actuation voltage is 25 V and the power consumption is 480 mW. This switch has a vast number of applications in the RF/microwave field, such as configurable voltage control oscillators, filters, and configurable matching networks. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

电容式RF开关介电电荷及相关可靠性模型及模拟

就介电电荷以及它对电容式RF MEMS开关可靠性的影响进行了分析,在前人的基础上建立起了一个更加全面和准确的介电电荷积累及其相关可靠性模型.介电电荷的产生是由于电介质中有漏电流(Ohmic电流、Frenkel-Poole电流),漏电流中电荷被介质陷阱捕获,进而导致电荷的积累.由此得到了介电电荷随时间的积累公式、开关失效寿命公式以及介电击穿寿命公式,其结果具有一定参考价值.     

A new analytical model for switching time of a perforated MEMS switch

In this paper, the design of a low-k meander based MEMS shunt capacitive switch with perforated beam meander has been presented. A closed form analytical model to calculate the switching time of designed structure is proposed. The model is based on modified Mejis and Fokkema’s capacitance model and linearization of non-linear electrostatic force on the switch beam. The model is utilized in evaluating the switching time for uniform as well as non-uniform serpentine meander designs, considering different values of actuation voltage and a wide variation of switching parameters. This work takes into account the beam perforation, fringing field and stiffness effect simultaneously altogether. The results obtained for both the meander designs under every design specifications has been found out to be less than or approximately equal to 100 µs. These model based results are then compared with 3D FEM simulated values. Comparative Analysis indicated that the model results and simulation results are in close agreement with each other.

     

The simulation and visual test contact process of a MEMS inertial switch with flexible electrodes

A MEMS inertial switch with flexible electrodes to contact-enhanced is designed and fabricated. ANSYS software is used to simulate the displacement of the mass, deformation of the flexible electrode and contact time of the switch. A high-speed video measurement has been used to visualize the switch contact process instead of electrical measurement for a deeper understanding of the dynamic contact process, and these images are used to visually validate simulation results. Comparisons between the simulation and image results are discussed. The image results are seen to be in good agreement with the dynamics simulation results.     

Design and simulation of RF MEMS shunt capacitive switch with non-uniform meanders for C-band applications

Microsystem Technologies - This paper presents, the design and simulation of RF MEMS shunt capacitive switch. The electromechanical and electromagnetic analysis of the switch has been done using...     

Schottky Barrier Contact-Based RF MEMS Switch

This paper presents the design, fabrication, and measurement results for a novel Schottky barrier contact-based radio frequency (RF) microelectromechanical systems (MEMS) switch. This Schottky barrier contact allows one not only to operate the RF MEMS switch in a traditional capacitive mode when it is reverse biased but also conduct current in a forward biased state. Forward biasing the switch recombines trapped charges, thus extending the lifetime of the switch. This paper intimately combines MEMS processing with solid-state electronics to produce a truly unique RF device.$hfill$[2008-0097]      

Reliability design of thermally actuated MEMS switches based on V-shape beams

This paper presents the design and fabrication of the thermally actuated MEMS switches based on out-of-plane V-beams. The purpose of this research is to analyze the mechanical response of a V-thermal actuator fabricated from aluminum in order to improve the accuracy in response and to increase the switch lifetime. The actuation of this kind of switches is based on the thermal displacement of the mobile electrode under thermal load that is generated when the actuation voltage is applied. It can be used either as a capacitive switch or as a metal-to-metal one. The displacement of the mobile electrode for a given temperature is analytically calculated and validated both numerically and experimentally. Experimental investigations are performed on a macro-scale sample using a 3D digital image correlation measuring system, a heating source and a thermal camera for temperature monitoring. The first fabrication steps of the MEMS switch based on the V-beam thermal actuator are presented. The out-of-plane V-beams thermal MEMS switches can be monolithically integrated in RF applications.

     

Design of novel compact anti-stiction and low insertion loss RF MEMS switch

A novel torsional RF MEMS capacitive switch design on silicon substrate is presented. The optimized switch topology such as reduction in up-state capacitance results in insertion loss better than ?0.1 dB till 20 GHz. Off to on state capacitance ratio is also improved by 18 fold and isolation is better than ?43 dB at 9.5 GHz. The achieved on state return loss is ?38 dB as compared to ?21 dB at 9.5 GHz. An optimized reduction in contact area and use of floating metal layer increases the switching speed from 56 to 46 μsec. It also increases the switch reliability by alleviating the stiction.     

Active Opening Force and Passive Contact Force Electrostatic Switches for Soft Metal Contact Materials

This paper reports on a mechanically bi-stable, electrostatically actuated switch mechanism with a large active opening force and a small passive closing force, designed to fit the contact and opening force requirements of soft contact materials such as gold. So far, most microelectromechanical systems (MEMS) switch designs have been optimized for a large contact force without paying too much attention to the opening force. In the “conventional,” most commonly used electrostatic microswitch concept, the force of the actuator is used to close the switch contacts, and the switch is opened by the passive restoring force of the deflected cantilever or membrane. This concept results in a large contact force, but the opening force is typically too small to overcome the contact adhesion force of soft metals, which makes this concept less suitable for contact materials such as gold with its low contact resistance at low contact forces. The switch concept presented in this paper is based on two cantilevers laterally moving by curved electrode actuators. The tips of the cantilevers are endowed with hooks which can be mechanically interlocked. In the latched state, the spring forces of the deflected cantilevers also act as the passive contact force between the switch contacts. The opening force is actively created by the curved-electrode actuators, which are utilized close to their best electromechanical operating point resulting in a maximum contact separation force. The theoretical discussion of the new concept as compared to conventional switch designs is supported by simulation results, measurements on fabricated devices, and by an analysis of exemplary switches published in the literature.1735     

An improved analytical model for static pull-in voltage of a flexured MEMS switch

Microsystem Technologies - This paper presents the design of low-k meander based MEMS shunt capacitive switch with beam perforations. A closed form model to accurately calculate the pull-in voltage...     

Analysis of RF MEMS shunt capacitive switch with uniform and non-uniform meanders

Microsystem Technologies - This paper reports on electromechanical, switching time and performance analysis of capacitive shunt RF MEMS switch with uniform and non-uniform meanders. The MEMS switch...     

折叠梁平面角对电容式RFMEMS开关性能的影响

低驱动电压电容式RFMEMS开关采用弹性拆叠梁支撑可变电容活动极板,使开关弹性结构具有很小的弹性系数,但也降低了开关的一阶模态谐振频率,致使开关无法获得较高的开关速度。提出了通过调整弹性折叠梁平面角微调弹性结构弹性系数的方法,在保证开关具有低驱动电压的同时,尽可能提高弹性结构的一阶模态谐振频率。仅改变弹性折叠梁平面角的大小,对其分别为0°,45°,90°的具体开关结构,应用MEMSCAD软件CoventorWare进行机电耦合仿真,定性分析了弹性折叠梁平面角对微结构弹性系数的影响。仿真结果表明：改变弹性折叠梁平面角大小,可以微调电容式RFMEMS开关的驱动电压和一阶模态谐振频率。     

基于分布式射频MEMS移相器电容开关的分析与设计

通过分析MEMS电容开关的工作原理,设计出一种适合分布式射频MEMS移相器电路的新型电容开关.采用Intel lisuiteTM软件优化电容开关的驱动电压、响应时间、释放时间和机械振动模式.结果表明,开关驱动电压为2.5 V、响应时间小于30μs,释放时间大于60 μs和所有振动模式固有频率都大于15 KHz.与普通开关结构比较,该新型电容开关结构具有优越射频机电性能和响应时间,同时也对电容开关的制备工艺进行分析.     

基于有限元法的MEMS加速度计热应力分析

残余应力对MEMS器件的力学性能、可靠性和寿命都有较大的影响。基于MEMS电容式加速度计,采用热结构耦合场分析方法,对热应力的影响进行了仿真分析,并和实验结果进行比较。结果表明热应力不是影响器件性能的主要因素,而仿真模型中未考虑到的一些物理因素和工艺误差则可能是主要因素。针对课题组加速度计的制备过程从工艺的角度提出了相应的改进措施,为加速度计温度补偿模型的完善以及改版设计提供参考。     

MEMS悬臂式开关的失效分析

介绍了一种表面微机械系统开关,悬臂材料为Au/SiOxNy/Au铬金作为电欧姆接触.用静电激励(激励电压为13 V)方式,测试其隔离度.获得结果为微机械开关在1～40 GHz的范围内隔离度可高达35 dB.我们采用对开关施加激励方波脉冲的方法测试寿命.结果寿命接近105,应用ANSYS对几种不同的MEMS射频接触悬臂开关模型进行了力电耦合分析和失效机理.     

Design and fabrication of implantable pressure sensing resistor sensor for human bladder monitoring system

Many aging people and patients have difficulties in bladder control. Recent methods have been studied for non-invasive measuring for bladder information. It must be improved to a more convenient and real time measurable system for accurately analyzing and controlling individual bladder information. This paper presents the pressure sensor for the invasive bladder monitoring system. The system has the pressure sensing resistor sensor (PSRS) which is set-up inside the bladder. The PSRS consists of a flexible and contactable diaphragm which deforms towards an underlying substrate while a range of pressure is applied. The flexible diaphragm has a thin metal film which acts as a switch and the underlying substrate has interdigitated electrodes which serve as a variable resistor. The PSRS initially exhibits infinite electrical resistance with no external pressure applied since the metal switch is not contact with the interdigitated electrodes. As the applied pressure increases above a threshold, the contact area increases thus the resistance of the PSRS decreases. Based on the finite element analysis, proper ranges for the diaphragm size and gap distance are determined. The sensor, the diaphragm size of which is 2.6 × 2.6 mm², has been fabricated through MEMS technology. The change of the electrical resistance is 0.5 Ω for the range of human bladder pressure (0–10 kPa). This PSRS will be effectively used for reliability and stability of the research for the improvement of bladder management. It can also be utilized for the future application.