硅基梳齿式MEMS器件及封装的失效调查

对典型硅基梳齿式MEMS器件进行失效调查和分析,验证其主要失效模式,分析其失效机理.利用电子扫描显微镜(SEM),X射线透视系统、扫描声学显微镜(SAM),X射线能谱成份分析(EDX)、金相切片分析、封装气体分析及电性能测试等分析技术,发现在工艺制造中的机械失效是造成此类器件失效的主要原因.另外,此类器件的封装失效主要表现为气密性失效和装配工艺失效.     

MEMS加速度计可靠性评价技术

MEMS加速度计是动作识别设备、姿态控制设备等电子设备的核心器件,其功能失效会严重影响设备的可靠性。而目前国内外还没有MEMS器件的可靠性实验标准,这在一定程度上制约了MEMS加速度计的应用与发展。针对该现状,深入研究了MEMS加速度计敏感部件的失效模式及失效机理,得到了典型环境应力与器件失效的关系,分析了加载环境应力可能导致器件失效的环境实验,并选取了相应的MEMS加速度计产品进行了可靠性实验验证,得出了MEMS加速度计可靠性评价的初步试行方案。     

微加速度计在冲击环境下的力学分析与仿真

微加速度计用于测量载体的加速度,并提供相关的速度和位移信息。该文主要对一种硅基压阻式高加速度g(g=9.8m/s2)值微加速度计在冲击加速度环境下进行有限元仿真分析。分析结果表明,所设计的压阻式高g值微加速度传感器在15×104 g量程内可正常并有效工作,且可承受40×104 g高速冲击,当加速度超过40.8×104 g时,加速度计发生失效变形。分析了加速度计在冲击环境下的主要失效模式及失效机理,得出了压阻式加速度计在冲击环境下的失效主要从梁与边框和质量块连接处开始,随着冲击时间(即冲击强度)的增加,结构应力逐渐达到屈服极限,材料发生屈服效应,然后发生断裂。     

三明治电容式MEMS加速度计的器件级真空封装

为了降低微电子机械系统(MEMS)加速度器件的热机械噪声,提高信噪比,使之能应用于石油勘探和地震监测中,对一种三明治式电容加速度传感器的器件级真空封装工艺进行了研究。这种器件级真空封装方法采用可编程高真空封装设备和MEMS工业中常用的材料、工艺,可适用于不同尺寸或布局的MEMS芯片。利用该封装方法,对一种采用自停止腐蚀工艺在中间质量块键合层上制作出2个对称"V"型槽的三明治式电容加速度计进行了真空封装,并对封装后的器件进行性能测试。结果表明,该加速度计在有吸气剂的情况下,品质因子(Q)可达到76,理论热机械噪声为0.026μg/槡Hz,腔体内部压强小于13 Pa,He气细漏检测漏率低于3×10-10Pa.m3/s,氟油粗漏无气泡,满足地震监测要求。     

MEMS器件在冲击下的可靠性

MEMS器件在制造、运输和使用过程中不可避免地受到不同程度的冲击作用,分析和认识MEMS器件在冲击下的响应和失效模式,对提高器件的耐冲击和可靠性具有一定的指导意义。本文综述了MEMS器件的冲击测试和理论分析方法,对MEMS器件的可靠性设计具有一定参考价值。     

微系统与中规模器件的封装技术设计

文章主要论述了微机电系统(MEMS)和微系统诸如微传感器、驱动器和微流体元件的电机封装技术、封装等级和封装技术相关的问题.首先陈述并讨论了典型的MEMS产品诸如微压传感器、加速度计和微泵;微电子封装和微系统封装技术,重点阐述芯片级封装技术和器件级封装技术问题.芯片级封装技术主要涉及芯片钝化、芯片隔离和芯片压焊;器件级封...     

EMC材料特性对MEMS加速度计封装可靠性的影响

采用有限元法分析了EMC(环氧模塑封材料)材料特性对MEMS(微电子机械系统)加速度计封装可靠性的影响.使用有限元软件ANSYS分别模拟了加速度计的输出电压、悬臂梁的挠度以及加速度计芯片的等效应力在温度循环载荷下的变化情况.结果发现,EMC的材料模式不同,MEMS加速度计的性能有明显差异.在使用EMC温度相关弹性模式和...     

一种用于MEMS超低值封装残余应力的测量方法

微机电系统(MEMS)封装残余应力是在封装工艺过程中芯片上产生的残余应力,它对于MEMS器件的热稳定性和长期贮存稳定性有着十分重大的影响,故而对MEMS封装残余应力的高精确度测量有利于封装应力的研究。由于封装残余应力十分微小,因此无法利用目前的测量手段直接测量封装应力,本文针对这个问题提出了一种基于应力放大结构和拉曼光谱法的封装应力测量方法,可以测量出MEMS器件中封装应力的平均水平。基于理论分析建立了原始封装模型与应力放大结构之间的放大关系,并提出应力放大结构的设计原则。接着采用3D有限元(FEM)仿真对一款高精确度MEMS微加速度计的封装应力测量进行了分析,其结果与理论分析具有很高吻合度。最后,针对该微加速度计的封装应力测量,成功制作了应力放大结构的芯片样片,并进行封装,随后拉曼光谱法被用于测量样片中的最大应力,进而计算出待测微加速度计中平均封装应力大小。实验结果与仿真分析具有很好的吻合度,证明本文所提出的测量方法具有相当的可靠性。     

一种基于低温共烧陶的无引线键合封装

为提高微机电系统(MEMS)加速度计的可靠性,减小因为引线键合断裂造成的传感器失效,该文设计了一种基于低温共烧陶瓷的无引线键合封装。该封装采用阳极键合技术将低温共烧陶瓷基板与芯片连接,同时将电路转接板同步集成。结果表明,该封装结构可减小传感器的封装尺寸,有效提高了MEMS加速度计的可靠性。     

高量程微加速度计的可靠性强化实验及分析

由于微加速度计的可靠性已经成为产品商业化过程中必须解决的一个重要问题,而冲击环境作用下导致微加速度计性能失效是微加速度计经常要面对的主要问题。针对高冲击对微加速度计破坏的影响进行可靠性研究。利用ANSYS有限元仿真进行分析初步得到失效模式和机理,设计并实施了微加速度计在冲击环境下的可靠性强化实验得到在冲击环境下的主要失效模式,并进行了相应分析,通过实验得到数据进行微加速度计的可靠性评估。通过可靠性强化实验进行验证,对微加速度计在冲击环境下的可靠性进行评估,并折算出在冲击影响作用下的平均寿命和可靠寿命以及绘制出其可靠度曲线。     

Flexible stop and double-cascaded stop to improve shock reliability of MEMS accelerometer

Flexible stop could provide shock protection for MEMS accelerometer. By modeling and simulation, the paper studied the response of a closed-loop MEMS accelerometer with stop under shock of different amplitudes and pulse width. Contact force plays an important role and the shock response shows strong nonlinearity due to the contact mechanism. A kind of double-cascaded stop is proposed to mitigate high-frequency shock failure. MEMS accelerometers with flexible stop and with double-cascaded stop are both designed and fabricated based on SOG (silicon on glass) technology. Compared with shock tests of accelerometers with hard cylinder stop, flexible stop could withstand more than 1e4 g shock with about 100 μs pulse width. Double-cascaded stop is more robust to high frequency shock.     

MEMS电容式加速度计的动态特性分析

针对梳齿电容形式的微机械加速度计,对其工作原理和动态性能进行了分析。该微结构的质量块由4个折叠梁支撑,采用梳齿结构形成差分检测电容用于检测质量块的位移。通过理论推导得到了结构的质量、刚度和阻尼的计算公式。组成梳齿结构的两平行极板间的气体在极板运动时产生两种作用力:阻尼力和弹性力,运动频率较低时阻尼力为主要表现形式,高频时弹性力则占主要因素。针对一组特定的结构参数,对气体压强分别为100Pa和0.1MPa时微机械加速度计的频率响应特性进行了分析,当气体压强太小时,会造成系统带宽的降低,而当气体压强较高时,系统的动态特性表现良好,并在电容极板间隙约为3μm时,系统的动态特性达到最优。     

硅MEMS器件键合强度在线检测方法

键合强度是MEMS器件研制中一个重要的工艺质量参数,键合强度检测对器件的可靠性具有十分重要的作用。为了获得MEMS器件制造工艺中的键合强度,提出了一种键合强度在线检测方法,并基于MEMS叉指式器件工艺介绍了一种新型键合强度检测结构;借助于材料力学的相关知识,推导出了键合强度计算公式,经过工艺实验,获得了键合强度检测数据;对获得的不同键合面积的键合强度加以对比,指出这些数据的较小差异,是由刻度盘最小刻度误差和尺度效应造成的。结合叉指式器件的工作环境,认为这种方法获得的键合强度更接近实际的工作情况。     

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.     

Single wafer encapsulation of MEMS devices

Packaging of micro-electro-mechanical systems (MEMS) devices has proven to be costly and complex, and it has been a significant barrier to the commercialization of MEMS. We present a packaging solution applicable to several common MEMS devices, such as inertial sensors and micromechanical resonators. It involves deposition of a 20 /spl mu/m layer of epi-polysilicon over unreleased devices to act as a sealing cap, release of the encapsulated parts via an HF vapor release process, and a final seal of the parts in 7 mbar (700 Pa) vacuum. Two types of accelerometers, piezoresistive and capacitive sensing, were fabricated. Piezoresistive accelerometers with a footprint smaller than 3 mm/sup 2/ had a resolution of 10 /spl mu/g//spl radic/Hz at 250 Hz. Capacitive accelerometers with a 1 mm/sup 2/ footprint had a resolution of 1 mg/spl radic/Hz over its 5 kHz bandwidth. Resonators with a quality factor as high as 14,000 and resonant frequency from 50 kHz to 10 MHz have also been built. More than 100 capacitive accelerometers and 100 resonators were tested, and greater than 90% of the resonators and accelerometers were functional.     

Reliability assessment of a MEMS microphone under mixed flowing gas environment and shock impact loading

In this work the reliability of a Micro-Electro-Mechanical Systems (MEMS) microphone is studied through two accelerated life tests, mixed flowing gas (MFG) testing and shock impact testing. The objective is to identify the associated failure mechanisms and improve the reliability of MEMS devices. Failure analyses are carried out by using various tools, such as optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS). Finite element analysis is also conducted to study the complex contact behaviors among the MEMS elements during shock impact testing. The predicted failure sites are in agreement with the experimental findings.     

基于梳齿间距偏差的硅微加速度计冲击与阶跃信号响应模型

源于概率统计理论,针对梳齿电容的微细加工偏差,给出了当各梳齿间距偏差在一定范围内独立且均匀分布时.单边电容和双边电容驱动的硅微加速度计冲击与阶跃信号响应物理模型.经过有限元仿真和Monte Carlo模拟验证,结果表明理论模型与仿真值之差小于10%.模型指出,当梳齿间距偏差由0变化到20%,加速度计在受到冲击与阶跃加速度信号作用时,其可靠工作范围将比无偏差理想情况下降10%～15%.该模型可望应用于实际有加工偏差的微加速度计可靠工作范围预先评估与设计.     

Failure mode analysis of MEMS suspended inductors under mechanical shock

Micro-electromechanical system (MEMS) suspended inductors have been widely studied in recent decades because of their excellent radio frequency performance. However, few studies have been performed on the failure analysis of MEMS suspended inductors under mechanical shock. In this study, the failure of MEMS suspended inductors with a planar spiral coil is investigated through analytical and experimental methods. We present a stress and deformation analysis to study the failure mode of the suspended inductors under shock. To verify the theoretical analysis, MEMS inductors are designed and fabricated, and shock tests are carried out. The shock tests show that the failure mode of the MEMS suspended inductors is a fracture that occurs at the ends of the inductor coil, and the test results agree with the theoretical analysis.