一种用于高机械可靠性RF MEMS开关制备的新型工艺

为提高介质桥串联接触式MEMS开关的工作寿命,本文改进了常规制备工艺,提出一种侧向钻蚀刻蚀介质桥膜下金属的方法,以获得平坦的介质桥膜,制备得到高机械可靠性的开关。与常规工艺相比,新工艺避免了应力集中问题,成品率从10％提高到了95％,工作寿命从1000次提高到了2500万次。在23.3V的驱动电压下,开关插入损耗 0.55dB＠DC-10GHz,隔离度 53.2dB＠DC-10GHz。     

用于制备高机械可靠性RF MEMS开关的新型工艺

对介质桥串联接触式RF MEMS开关的制备工艺进行了研究.介绍了开关的结构,说明了采用常规制备工艺容易在桥膜上形成应力集中,严重影响开关的机械可靠性.通过改进工艺,提出了一种侧向钻蚀刻蚀介质桥膜下金属的方法,获得了平坦的介质桥膜.最后,给出了完整的开关制备流程.与常规工艺相比,新工艺避免了应力集中问题,提高了开关的机械可靠性,成品率从10%提高到了95%,工作寿命从1 000次提高到了2.5×107次.此外,在23.3 V的驱动电压下,开关插入损耗＜0.55 dB＠DC-10 GHz,隔离度＞53.2 dB＠DC-10 GHz.结果表明该工艺可满足无线通讯对MEMS开关成品率、寿命和微波性能的要求.     

欧姆龙推出RF MEMS开关产品

日本欧姆龙公司推出了用于半导体测试仪及高频（RF）测量设备的RFMEMS开关，该产品为支持10GHz高频传输的单刀双掷（SPDT）开关，实现了2004年制定的实用化目标——具有可开关1亿次的可靠性，计划用于手机、半导体测量仪及测量设备等。     

RF MEMS开关在开关瞬态时的电磁干扰

针对RF MEMS开关在开和关瞬态时的充电和放电的过程中的开关电容的变化、极板间电场的变化以及因此而产生的磁场进行了详尽的推导,沈明在开关的瞬态产生的变化电磁场将对信号产生一定程度的干扰.     

驱动信号与微波信号物理隔离的RF MEMS开关的研究

针对MEMS开关在宽带应用时遇到的驱动信号与微波信号间的干扰问题,论述了驱动信号与微波信号物理隔离的多种开关的设计,分析了4种结构形式的MEMS开关,使用IntelliSuite○R软件进行开关机电耦合分析。在开关总的结构尺寸确定的前提下,使用ADS/Momentum场分析软件,微调膜桥和梁的结构参数,通过通孔接地实现微带线与CPWG信号的连接,通过驱动电极的结构和连接方式及与微波信号线间隙的调整,实现了MEMS开关整体性能的优化。     

基于MEMS技术的通信器件及其应用

微电子机械系统是一种新兴技术,它几乎影响着每一个科学技术领域,如交通、无线通信、航天、化学以及光波系统。目前许多工业领域期待选用微电子机械系统来解决技术上的问题。以下简述了微电子机械系统技术的基础概念、所用材料、加工工艺等;重点综述了基于MEMS技术的通信器件及其应。     

静电式MEMS光开关新器件设计开发流程

在研究MEMS集成系统设计经验的基础上,简要论述了设计流程在MEMS设计中的重要性,提出静电式光开关新器件的开发流程,并以悬臂梁式MEMS光开关为例,进行了理论分析、静电-结构耦合场分析、材料选择、结构参数优化和控制电路设计等方面的研究.所提出的设计开发流程也适用于静电驱动的其他器件的开发,如RF-MEMS器件.     

Ku-波段MEMS单刀双掷开关的设计与模拟

利用Ku-波段MEMS单刀单掷膜开关和成熟的微带线技术设计了一种Ku-波段MEMS单刀双掷膜开关.模拟结果为阈值电压19V左右,工作于Ku-波段(8～12)GHz,在中心频率15GHz处,导通开关的插入损耗为-0.15dB,截止开关的隔离度为-33dB,开关的回波损耗为-27dB.     

无源MEMS压力开关的设计与制备

为了克服传统机械式和电子式压力开关的体积大、制作工艺复杂以及不易与后续电路集成等缺点,论文采用具有金属引线台阶覆盖能力的玻璃浆料封装技术进行了无源MEMS压力开关的设计和制备。设计的无源MEMS压力开关的整体结构方案主要包括硅盖板上的压力敏感膜、硅岛、上电极和微阻挡凸台以及玻璃基底上的玻璃浆料和下电极。通过仿真优化了压力敏感膜、硅岛和上下电极的关键尺寸。经过三次湿法腐蚀工艺流程制得了双阻挡凸台、硅岛和感压膜片。通过玻璃浆料热压工艺将硅盖片、玻璃基底和金属引线三者键合成一体,工艺结果显示双阻挡凸台的高度和感压膜片的厚度很好地控制在8μm和50μm,而且经测试,MEMS压力开关的阈值压力为125kPa。     

射频MEMS开关的研究

概述射频MEMS开关的研究背景及意义,介绍国内外射频MEMS开关的研究现状,列举出两种主要的射频MEMS开关：电容耦合并联式开关和金属．金属接触串联式开关的结构、工作原理、性能比较。     

射频系统中MEMS谐振器和滤波器

介绍了目前国内外射频系统中所涉及的静电梳状谐振器、自由梁谐振器、薄膜声体波谐振器、腔结构谐振器、平行谐振器结构HF带通滤波器、折叠梁MF滤波器、分布传输线可调滤波器等MEMS谐振、滤波器件.对这些器件的结构原理、制造方法以及性能指标作了分析.把这些器件的性能指标和目前射频系统中谐振器、滤波器的性能要求进行比较,分析了这些器件的应用前景.最后,对基于MEMS技术的射频谐振器、滤波器发展作出展望.     

基于腔结构的射频微机械谐振元件的设计

对圆柱形复合腔结构微机械谐振元件进行了设计研究,提出了一种基于柱形腔结构的微机械复合谐振元件的设计方法,并对其结构及特性进行了研究.建立了复合腔结构的电磁场数学方程,腔体基于体微机械微细加工技术实现工艺设计,最后对该元件进行了仿真分析.TM010模式下,谐振腔谐振频率为24.313299GHz,Q值为3529.707890,考虑微带耦合时仿真出复合谐振元件的最佳谐振频率为24.75GHz.仿真实验结果和理论值的平均误差不到1%,两者吻合得很好,说明了该设计的可行性.进一步改变结构参数,可获取不同谐振频率的器件,且可在腔体中填充高介电常数介质来减小器件的谐振频率,克服了以往使用腔体结构在低频段时体积过大等问题.     

Failure Mechanisms of Capacitive MEMS RF Switch Contacts

Microelectromechanical systems (MEMS) radio frequency (RF) switches hold great promise in a myriad of commercial, aerospace, and military applications. In particular, capacitive type switches with metal-to-dielectric contacts (typically Au- on-silicon nitride) are suitable for high frequency (≥10 GHz) applications. However, there is little fundamental understanding of the factors determining the performance and reliability of these devices. To address this void in understanding, we conducted fundamental studies of Au-on-Si₃N₄ contacts at various bias voltages using a micro/nanoadhesion apparatus as a switch simulator. The experiments were conducted in air at 45% relative humidity. The switch simulator allows us to measure fundamental parameters such as contact force and adhesion, which cannot be directly measured with actual MEMS switches. Adhesion was found to be the primary failure mechanism. Both a mechanical and electrical effect contributed to high adhesion. The mechanical effect is adhesion growth with cycling due to surface smoothening, which allows increased van der Waals interaction. The electrical effect on adhesion is due to electrostatic force associated with excess charge trapped in the dielectric, and was only observed at 40 V bias and above. The two effects are additive, but the electrical effect was not present until surfaces were worn smooth by cycling. Surface smoothening increases the electric field in the dielectric, which leads to trapped charge and higher adhesion. Excessive adhesion can explain decreased lifetime at high bias voltage previously reported with actual capacitive MEMS switches. Aging of open contacts in air was found to reduce adhesion. Surface analysis data show the presence and growth (in air) of an adventitious film containing carbon and oxygen. The adventitious film is responsible for aging related adhesion reduction by increasing surface separation and/or reducing surface energy. No junction growth and force relaxation with time were observed in capacitive switch contacts, as was previously observed with Au–Au contacts at low current in direct current MEMS switches.     

Fundamental studies of Au contacts in MEMS RF switches

Microelectromechanical systems (MEMS) radio frequency (RF) switches hold great promise in a myriad of commercial, aerospace, and military applications. However, there is little understanding of the factors determining the performance and reliability of these devices. Fundamental studies of hot-switched gold (Au) contacts were conducted using a micro/nanoadhesion apparatus as a switch simulator. Experiments were conducted in a well defined air environment under precisely controlled operating conditions. Fundamental properties were connected to performance with an emphasis on the effects of contact force and electric current on contact resistance (R), microadhesion, and reliability/durability. Electric current had the most profound effect on switch performance. Observations at low current (1–10 A) include: (1) slightly higher R; (2) asperity creep; (3) high adhesion after rapid switching; (4) switch bouncing; and (5) reasonable durability. Conversely, observations at high current (1–10 mA) include: (1) slightly lower R; (2) melting; (3) no measurable adhesion; (4) less propensity for switch bouncing; (5) necking of contacts; and (6) poor reliability and durability due to switch shorting. Low current behavior was dominated by the propensity to form smooth surface contacts by hammering, which led to high van der Waals force. High current behavior was dominated by the formation of Au nanowires that bridge the contact during separation. Data suggest the presence of an adventitious film containing carbon and oxygen. Aging of the contacts in air was found to reduce adhesion.     

基于柔性止动的MEMS惯性开关冲击可靠性强化

为了提高MEMS惯性开关的冲击可靠性,提出了一种柔性止动结构。首先,利用连续接触力理论建立了止动碰撞模型,通过Simulink对模型进行仿真,研究开关在不同止动形式下的响应特性。接着,从空间占用和应力集中的角度对悬臂梁和平面微弹簧两种止动形式进行讨论,设计止动结构。最后,利用UV-LIGA工艺制作开关样机,通过落锤冲击系统对样机进行测试。碰撞接触力对于冲击可靠性至关重要,Simulink仿真结果表明柔性止动结构能够极大的延长碰撞接触时间,从而降低接触力。同时,采用柔性止动还改善了碰撞后的弹跳现象,提高闭锁稳定性。冲击试验表明,开关累积失效分布函数符合韦布尔分布,标度参数(参考加速度)α=29 600、形状参数β=8.2。相比无柔性止动的MEMS开关,提出的柔性止动明显改善了开关的抗冲击性能。对柔性止动的建模、仿真与试验为MEMS惯性开关的抗冲击设计提供了有益参考。