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.     

Comprehensive Warpage Analysis of Stacked Die MEMS Package in Accelerometer Application

<正>Packaging of MEMS ( micro-electro-mechanical system ) devices poses more challenges than conventional IC packaging, since the performance of the MEMS devices is highly dependent on packaging processes. A Land Grid Array ( LGA ) package is introduced for MEMS technology based linear multi-axis accelerometers. Finite element modeling is conducted to simulate the warpage behavior of the LGA packages. A method to correlate the package warpage to matrix block warpage has been developed. Warpage for both package and sensor substrate are obtained. Warpage predicted by simulation correlates very well with experimental measurements. Based on this validated method, detailed design analysis with different package geometrical variations are carried out to optimize the package design. With the optimized package structure, the packaging effect on accelerometer signal performance is well controlled.     

A wafer-level microcap array to enable high-yield microsystem packaging

Packaging represents a significant and expensive obstacle in commercializing microsystem technology (MST) devices such as microelectromechanical systems (MEMS), microopticalelectromechanical systems (MOEMS), microsensors, microactuators, and other micromachined devices. This paper describes a novel wafer-level protection method for MSTs which facilitate improved manufacturing throughput and automation in package assembly, wafer-level testing of devices, and enhanced device performance. The method involves the use of a wafer-sized microcap array. This array consists of an assortment of small caps molded onto a material with adjustable shapes and sizes to serve as protective structures against the hostile environments associated with packaging. It may also include modifications which enhance its adhesion to the MST wafer or increase the MST device function. Depending on the application, the micromolded cap can be designed and modified to facilitate additional functions, such as optical, electrical, mechanical, and chemical functions, which are not easily achieved in the device by traditional means. The fabrication and materials selection of the microcap device is discussed in this paper. The results of wafer-level microcap packaging demonstrations are also presented.     

Multi-scale analysis of polysilicon MEMS sensors subject to accidental drops: Effect of packaging

The effect of packaging on the impact-carrying capacity of micro electro-mechanical systems (MEMS) is investigated, with specific reference to a translational accelerometer. By exploiting the small ratio between the masses of MEMS and package/die (typically 10⁻³ or less) a decoupled two-scale, finite element approach is adopted: at the package/die length-scale the dynamics of whole device after the impact against a flat target surface is studied; at the sensor length-scale the response of the MEMS to the drop-induced loading is investigated, and MEMS details where the stress state can exceed the tensile strength of polysilicon are identified. Two drop orientations are considered, here termed bottom and top; in the first case, package and die strike the target with their bottom surfaces; in the second case, they fall upside-down, and strike the target with their top surfaces.By comparing the simulation outcomes in terms of maximum attained tensile stress, it results that package does not always lead to benefits in term of capability of the studied sensor to sustain drops. In the bottom drop configuration, e.g. MEMS failure may be triggered by the package.     

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。     

MEMS加速计的SOIC封装技术研究

文中通过研究MEMS（微机电系统）加速计在SOIC封装（小外形集成电路封装）下的特性,针对MEMS芯片断裂故障的原因分析了影响PPM（百万分比的缺陷率）性能的主要封装工艺步骤。其中感应单元固晶胶的硬度是引起芯片断裂的主要参数,通过反向工程确定了可以同时满足感应单元固有频率和封装可靠性要求的固晶材料。在试验中采用固晶胶E后,MEMS加速计的SOIC封装呈现出更加强韧的特性。此研究对于改善MEMS加速计的PPM性能有一定参考价值。     

Wafer-level packaging of silicon to glass with a BCB intermediate layer using localised laser heating

Adhesive wafer-level bonding is an excellent solution to meet the stringent requirements in micro-electro-mechanical systems (MEMS) packaging, one of the challenges in MEMS manufacturing, in a steadily growing micro-systems market. A range of bonding processes for commercially available substrate bonders have been developed, which apply global heating during the bonding procedure. This article, however, describes an approach where heating is kept to a minimum by combining the merits of laser joining, a truly localised heating technique, and adhesive wafer-level bonding. This unique bonding technique, which enables the use of temperature-sensitive materials within the package, is demonstrated for bonding of silicon to glass - materials commonly used in MEMS fabrication - with a benzocyclobutene (BCB) intermediate bonding layer. As a proof of concept for wafer-level packaging, bonding of two simplified patterns is demonstrated, one with five individual samples on the same wafer, and the other with nine samples. To verify the influence of this innovative bonding technique on the quality of the seal the devices are shear force tested and the results are compared with those of devices packaged at chip-level.     

MEMS仿生矢量水听器封装结构的隔振研究

利用隔振原理,设计了矢量水声传感器系统中一种新型隔振封装结构模型,即加入橡胶减振器的新型封装结构。采用ANSYS软件对封装模型进行模态分析,研究模型结构和几何尺寸对其隔振性能的影响,确定最优隔振封装结构;对模型的几何尺寸及橡胶隔震材料力学参数进行优化,并对优化模型的隔振性能进行实验测试和评估。实验结果表明：所设计的新型橡胶减振结构具有一定的减振效果,隔离了一定程度的核心器件以外的外界振动干扰,提高了原有封装结构矢量水听器的探测灵敏度。再次验证了硅微MEMS仿生矢量水声传感器不但体积小、质量轻、结构简单,而且具有低频灵敏度高等优点。     

A Novel Wafer-Level Hermetic Packaging for MEMS Devices

Some emerging microelectromechanical systems (MEMS) devices such as high-performance inertial sensors and high-speed actuators must be operated in a high vacuum and in order to create this vacuum environment, specific packaging is required. To satisfy this demand, this paper presents a novel method for hermetic and near-vacuum packaging of MEMS devices. We use wafer-level bonding technology to combine with vacuum packaging, simultaneously. For this packaging solution, the wafers with air-guided micro-through-holes were placed on a custom-built design housed in a vacuum chamber maintained at a low-pressure environment of sub-10 mtorr. Packaging structure is then sealed by solder ball reflow process with the lower heating temperature of 300degC to fill up micro-through-hole. Experimental results shown the hermetical packaging technique using solder sealing is adapted to the wafer-level microfabrication process for MEMS devices and can achieve better yield and performance. Thus, this technique is very useful for many applications with high performance and low packaging cost can be obtained due to wafer-level processing.     

MEMS器件的封装材料与封装工艺

随着各种MEMS新产品的不断问世,先进的MEMS器件的封装技术正在研发之中.本研究综述了MEMS的封装材料,包括陶瓷、塑料、金属材料和金属基复合材料等.阐述了MEMS的主要封装工艺和技术,包括圆片级封装、单芯片封装、多芯片组件和3D堆叠式封装等.并展望了MEMS器件封装的应用和发展前景.     

用于MEMS器件芯片级封装的金-硅键合技术研究

MEMS器件大都含有可动的硅结构 ,在器件加工过程中 ,特别是在封装过程中极易受损 ,大大影响器件的成品率。如果能在MEMS器件可动结构完成以后 ,加上一层封盖保护 ,可以显著提高器件的成品率和可靠性。本文提出了一种用于MEMS芯片封盖保护的金 硅键合新结构 ,实验证明此方法简单实用 ,效果良好。该技术与器件制造工艺兼容 ,键合温度低 ,有足够的键合强度 ,不损坏器件结构 ,实现了MEMS器件的芯片级封装。我们已经将此技术成功地应用于射流陀螺的制造工艺中     

Deformation Behavior of MEMS Gyroscope Sensor Package Subjected to Temperature Change

In microelectromechanical system (MEMS) devices, the deformation of MEMS structure caused by packaging induced stress is of great concern since it directly affects the performance of the device. In this paper, deformation behavior of the MEMS gyroscope package subjected to temperature change is investigated using a high-sensitivity moire interferometry. Temperature dependent analyses of warpage and extension/contraction of the package are presented. Analysis of the package reveals that global bending deformation occurs due to the mismatch of the coefficient of thermal expansion between the chip, the molding compound, and the printed circuit board. Detailed global and local deformations of the package by temperature change are investigated, and their effect on the frequency shift of the MEMS gyroscope is studied. It is found that package deformation or package induced stress results in the frequency shift of the MEMS gyroscope structure. In order to increase robustness of the structure against deformation, a "crab-leg" type spring is replaced with a semi-folded spring. The results show that the frequency shift is greatly reduced after applying the semi-folded spring. This frequency shift is within the tolerance limit of the gyroscope sensor in this work     

A wafer-level hermetic encapsulation for MEMS manufacture application

In order to simplify the processing complexity and cut down the manufacturing cost, a new wafer bonding technique using ultraviolet (UV) curable adhesive is introduced here for microelectromechanical systems (MEMS) device packaging and manufacturing applications. UV curable adhesive is cured through UV light exposure without any heating process that is suitable for the packaging of temperature-sensitive materials or devices. A Pyrex 7740 glass is chemically wet etched to form microcavities and utilized as the protection cap substrate. After a UV-curable adhesive is spin-coated onto the glass substrate, the substrate is then aligned and bonded through UV light exposure with a device substrate below. Electrical contact pad opening and die separation are done simultaneously by dicing. Two different testing devices, a dew point sensor and capacitive accelerometer, are built to evaluate the package strength and hermeticity. After the dicing process, no structural damage or stiction phenomenon is found in the packaged parallel capacitor. The acceleration test results also indicate that the package using the Loctite 3491 UV adhesive with 150 /spl mu/m bond width can survive more than 300 days at a 25/spl deg/C and 100% relative humidity working environment.     

电子元器件封装技术发展趋势

晶圆级封装、多芯片封装、系统封装和三维叠层封装是近几年来迅速发展的新型封装方式,在推动更高性能、更低功耗、更低成本和更小形状因子的产品上,先进封装技术发挥着至关重要的作用。晶圆级芯片尺寸封装(WCSP)应用范围在不断扩展,无源器件、分立器件、RF和存储器的比例不断提高。随着芯片尺寸和引脚数目的增加,板级可靠性成为一大挑战。系统封装(SIP)已经开始集成MEMS器件、逻辑电路和特定应用电路。使用TSV的三维封装技术可以为MEMS器件与其他芯片的叠层提供解决方案。     

MEMS封装技术及设备

概述了进入后摩尔时代的MEMS技术,通过TSV技术整合MEMS与CMOS制程,使得半导体与MEMS产业的发展由于技术的整合而出现新的商机。主要介绍了MEMS器件封装所面临的挑战及相应的封装设备。     

IC封装中互连线信号完整性的研究

随着电子芯片向着高密度、高频率和小体积化方向发展,IC封装的结构尺寸及其互连线系统在信号完整性、损耗等多方面影响着整个电路系统的可靠性。因此,对IC封装及其互连线电特性的分析显得尤为重要。文章以四列直插芯片封装外壳模型为设计实例,利用AnsoftQ3D软件提取了该封装模型的寄生电阻、电容和电感（RCL）,并结合Mult...     

一种用于胎压传感器的新型系统级封装技术

TPMS IC是TPMS系统模块的关键核心器件,需要采用系统级封装(SiP)技术。对TPMS IC的一种新型SiP封装技术作了研究分析。在引线框架上引入电路板中介层,改善了芯片间电气互连与分布,增大了引入薄膜电阻电容元件的设计弹性。采用预成型模制部分芯片的封装技术,满足了IC与MEMS芯片不同的封装要求,还增强了SiP产品的可测试性和故障可分析性。采用敞口模封、灌装低应力弹性凝胶和传感器校准测试相结合的方法有效避免封装应力对MEMS压力传感器的影响。     

Modeling Package-Induced Effects on Molded Hall Sensors

The consideration of package-induced effects during the design process of microelectromechanical systems (MEMS) sensors is still of major importance in order to estimate its influence on performance and reliability. A method for predicting the influence of the packaging and assembly process on the performance of a Hall sensor is described. The geometry of the device, the behavior of the packaging materials, as well as the packaging process are regarded using this method. At first, the complex material behavior of adhesives and molding compounds was investigated. It is shown, that for modeling the influence of the packaging on the sensor performance correctly, the nonlinear temperature- and time-dependent material behavior has to be taken into account. Differences of the coefficients of thermal expansion of the packaging materials lead to thermo-mechanical stress in the package. Due to the time-dependent material properties, this results in a change of the offset and the sensitivity of the sensor over time and may lead to a sensor working outside its specification. The piezoresistive and piezo-Hall coefficients of semiconductor Hall plates were measured; thereby the stress- and temperature-dependency of the Hall plates were determined. According to the results, package-induced stresses lead to a change of the offset voltage up to 80% of the full-scale while the sensitivity changes by $pm$4 percentage.      

Microelectromechanical systems and system-on-chip connectivity

The interconnection of microelectromechanical systems (MEMS) and other devices to a system-on-chip (SoC) implementation is described. MEMS technology can be used to fabricate both application specific devices and the associated micropackaging system that will allow for the integration of devices or circuits, made with non-compatible technologies, with a SoC environment. In the primary example presented, MEMS technology has been used to develop an acoustical array sensor for a hearing instrument application and also to provide a custom micropackaging solution suitable for in-the-ear canal implantation. A MEMS based modular micropackaging solution consisting of MEMS socket submodules and an insertable/removable microbus card has been developed to provide the necessary packaging and connectivity requirements. The modular socket concept can also be used for many other purposes, such as temporarily connecting a CMOS die to a SoC implementation of a die tester using MEMS based cantilevered bridge-type microspring contacts to provide connectivity to the die under test.     

MEMS封装技术的发展及应用

封装技术在微电子机械系统(MEMS)器件中的地位和作用越来越重要。本文归纳与总结了MEMS封装的特点和发展趋势,重点对MEMS封装技术的应用进行了分析,最后给出一些有益的想法和看法。