硼硅玻璃与硅阳极键合界面形成机理分析

对硼硅玻璃与硅进行了阳极键合实验,通过扫描电镜对键合界面的微观结构进行分析表明:玻璃/硅的键合界面有明显的中间过渡层生成;分析认为电场力作用下玻璃耗尽层中的氧负离子向界面迁移扩散并与硅发生氧化反应是形成中间过渡层的主要原因,而界面过渡层的形成是硅/玻璃界面键合实现永久连接的直接原因.     

玻璃与铝在不同层数结构下的阳极键合界面力学性能

运用共阳极法实现不同层数玻璃／铝的阳极键合,采用MARC非线性有限元分析软件,对三层、五层、七层、九层玻璃／铝键合试件的界面力学性能进行比较分析,探讨结合处残余应力随层数增加的变化趋势,分析结果表明,由于多层结构的对称性,最大的等效应力发生在中心处的过渡层。研究结果为MEMS器件在多层封装结构的设计提供了理论依据。     

面向超高温压力传感器的SiC-SiC键合方法

为了实现耐高温压力传感器SiC腔体的制作,分别利用高性能陶瓷胶、旋涂玻璃和金属Ni等3种材料作为键合层,研究了SiC-SiC键合工艺.扫描电子显微镜和键合拉伸强度实验结果表明,这3种材料的键合层均可以成功应用于SiC-SiC键合,其中高性能陶瓷胶键合层厚度为20~30μm,键合强度可达4 MPa;旋涂玻璃键合层厚度为2μm左右,键合强度约1.5 MPa;金属Ni键合层厚度为1μm,键合强度约为0.5 MPa.     

功能陶瓷（玻璃）与金属材料阳极键合的机理研究及应用进展

阐述了功能陶瓷、玻璃等无机非金属材料与金属及半导体材料进行阳极键合的键合机理、在MEMS中的应用及其发展前景；列举了阳极键合在MEMS生产过程中的一些最新应用实例；指出了其在MEMS的生产制造过程中存在的一些问题及今后的研究方向。     

Pyrex玻璃／铝多层阳极键合界面结构与力学分析

采用公共阳极法实现了Pyrex玻璃与铝多层晶片的静电键合,对玻璃/铝/玻璃阳极接舍界面的组织结构及其连接机理和力学特征进行了重点研究.分别利用微拉伸测试设备和ANSYS软件分析了连接区的力学性能和残余应力分布特征.分析认为键合区由玻璃一过渡层一铝组成,过渡层为Al2O3-SiO2复合氧化物.玻璃/铝界面的微观组织和元素分布均以铝为对称轴呈对称分布.在玻璃/铝/玻璃多层连接区,键合界面附近的残余应力和应变呈对称分布,多层结构的对称性有利于缓解接头应变和应力,表明应用公共阳极法可实现多层玻璃/铝/玻璃的良好键合.     

电子束蒸发玻璃薄膜中间层的阳极键合研究

介绍了一种用电子束蒸发Schott 8329玻璃薄膜作为中间层,实现硅-硅以及硅-SOI阳极键合的方法.调整蒸发时的工艺并且450℃退火,沉积了粗糙度9.62 nm、初始应力139 MPa、喷点较少的薄膜,从而获得了＞95%的键合面积.键合电压20 V,温度300℃～500℃下硅-硅的键合强度可达1.47 J/m2,同时分析了键合电流特性.400℃,40V下键合了Si和SIMOX SOI硅片,用TMAH溶液进行基底减薄,获得了厚介质层薄顶层硅结构,这为一些MEMS器件的制作奠定了基础.     

阳极键合研究现状及影响因素

为了提高键合质量、优化键合材料,促进阳极键合技术在工业生产中的应用,本文以“硅/玻璃”的阳极键合为例,阐述了阳极键合作为新型连接工艺的键合机理及工艺过程,介绍了现阶段阳极键合在国内外工业生产中的应用实例及相关研究,尤其是在微电子封装领域所展现的杰出应用前景,同时结合阳极键合过程中对键合参数、材料处理等要求,给出了影响键合质量的各种因素,以及在键合过程中常出现的问题及其解决办法.本文立足于键合机理及键合工艺过程,结合不同材料特性,重点阐述了阳极键合这一新型连接工艺的国内外研究现状及影响键合的因素,为进一步提高键合质量、优化键合工艺、开发新的键合材料等提供理论依据.     

功能陶瓷(玻璃)与金属材料阳极键合的机理研究及应用进展

阐述了功能陶瓷、玻璃等无机非金属材料与金属及半导体材料进行阳极键合的键合机理、在MEMS中的应用及其发展前景;列举了阳极键合在MEMS生产过程中的一些最新应用实例;指出了其在MEMS的生产制造过程中存在的一些问题及今后的研究方向.     

一种避免静电黏附失效的低应力阳极键合技术

基于阳极键合过程中的静电吸合效应,提出了一种可避免静电黏附失效的低应力阳极键合技术.采用湿法腐蚀技术制作了梯形截面的硅梁结构和对应的Pyrex玻璃基底,理论分析了该结构的静电吸合电压并进行了实验验证.采用铝/铬作为玻璃基底的电极层,铬作为中间层,从而阻止阳极键合发生.由于在键合过程中形成的铬氧化物为导体,所以硅与玻璃之间的静电场消失,从而阻止了玻璃中的O2-等负离子向硅移动,避免了静电黏附失效;采用Al作为主要电极层,可以保证电极的电学特性.采用了逐步升压法,首先在200 V低电压条件下进行预键合,使结合面具有一定的连接强度,然后再提升键合电压至400 V进行强化键合,在充分保证键合强度的前提下,静电力作用下的结构变形仅为400 V恒压模式下的1/4,减小了静电力对键合结构产生的影响,有效改善了键合过程中产生的残余应力.     

Microelectromechanical system pressure sensor integrated onto optical fiber by anodic bonding

Optical microelectromechanical system pressure sensors based on the principle of Fabry-Perot interferometry have been developed and fabricated using the technique of silicon-to-silicon anodic bonding. The pressure sensor is then integrated onto an optical fiber by a novel technique of anodic bonding without use of any adhesives. In this anodic bonding technique we use ultrathin silicon of thickness 10 microm to bond the optical fiber to the sensor head. The ultrathin silicon plays the role of a stress-reducing layer, which helps the bonding of an optical fiber to silicon having conventional wafer thickness. The pressure-sensing membrane is formed by 8 microm thick ultrathin silicon acting as a membrane, thus eliminating the need for bulk silicon etching. The pressure sensor integrated onto an optical fiber is tested for static response, and experimental results indicate degradation in the fringe visibility of the Fabry-Perot interferometer. This effect was mainly due to divergent light rays from the fiber degrading the fringe visibility. This effect is demonstrated in brief by an analytical model.     

A multichannel microfluidic sensor that detects anodic redox reactions indirectly using anodic electrogenerated chemiluminescence

Here, we describe a new approach for detecting redoxactive targets by electrochemical oxidation and reporting their presence by electrogenerated chemiluminescence (ECL) based on electrochemical oxidation of Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) and tripropylamine (TPA). This new strategy, which complements our previous reports of using ECL to signal the presence of targets undergoing electrochemical reduction, takes advantage of many of the attractive attributes of microfluidic-based electrochemical cells. These attributes include close proximity of multiple flow channels and electrodes, ability to move reagents through channels under laminar flow conditions, and the capacity to precisely place device components relative to one another using photolithography. Specifically, the microfluidic electrochemical sensor described here consists of three channels. The analyte and ECL reporting cocktail flow through separate channels, but they share a common anode. The cathode resides in a channel containing a sacrificial reductant. In this configuration, the target analyte competes with Ru(bpy)3(2+) and TPA to provide electrons for the reductant. Accordingly, in this competitive assay approach, the presence of the analyte is signaled as a lowering of the ECL intensity. In this report, the device performance characteristics are reported, and the detection of both ferrocyanide and dopamine is demonstrated at micromolar concentrations.     

基于正交试验分析的阳极键合强度研究

采用抗拉强度作为键合质量评价的指标,对硅-玻璃阳极键合的键合温度、冷却速度、退火温度和时间等四个参数的三个位级下的键合效果进行了分析。通过采用正交试验分析法,将81组试验减少为9组并进行了试验。采用自制的抗拉强度测试机对强度进行了测试,结果发现,阳极键合后的冷却速度对强度的影响最为显著,冷却速度越低,强度越高。最后对断裂面进行了SEM分析并对试验结果进行了讨论。     

Residual stress mapping of epoxy molding compound in a ball grid array microelectronic package using a fluorescent sensor

Thermal residual stresses developed at the time of semiconductor molding may cause serious problems both in their structural and functional performance; therefore, residual stress assessment in microelectronic devices is a mandatory evaluation step. Fluorescence piezo-spectroscopy was applied to evaluate residual stresses with a microscopic resolution inside a semiconductor encapsulant. In order to obtain reliable stress information, a low fraction of alumina powder, as a fluorescent sensor, was embedded into the silica/epoxy molding compound. Residual stress was transferred from the molding compound to the alumina phase and could be monitored by recording the shift of the sharp and intense fluorescence spectrum of Cr3+ in alumina. Two-dimensional residual-stress maps, recorded near the edge of the silicon chip, revealed a strong stress concentration in the molding compound. Experimental results were compared with calculations obtained by the linear finite element method. Such a comparison showed that the experimental stress values were systematically larger than the corresponding calculated values due to local delamination at the chip edge.     

Residual stress development during the composite patch bonding process: measurement and modeling

This paper presents an experimental technique for monitoring residual stress development throughout the composite patch repair curing process. Using this technique, process-induced strains and specimen warpage during a number of different cure cycles were measured for a simulated single-sided composite patch repair of an aluminum substrate. Models for adhesive cure rate and glass transition behavior of the patch adhesive resin (FM 300-1K) were combined with a simple bi-metallic strip model to predict specimen warpage and strain behavior during cure. Model predictions were compared with experimental measurements and were used to assist in the development of optimized cure cycles. Using these optimized cycles, it was found that it was possible to achieve significant (>20%) reductions in patch warpage and at the same time, minimize processing time and obtain a high final adhesive degree of cure. Experimental observations suggest that an improved patch model incorporating adhesive viscoelastic behavior during cure would assist in achieving additional process improvements.     

High-resolution photoelastic pressure sensor using low-birefringence fiber

The effect of birefringence induced in a single-mode fiber by a lateral force has been applied to measure the absolute value of force or pressure with high resolution. A sensor configuration with an extended detecting surface has been investigated by means of calibrated weights. The sensor is sensitive to an incremental force of 2 x 10(-3) N, independently of the length of the fiber. The maximum force applied was 10 N/m of fiber length.     

An intelligent pressure sensor using neural networks

In this paper, we propose a scheme of an intelligent capacitive pressure sensor (CPS) using an artificial neural network (ANN). A switched-capacitor circuit (SCC) converts the change in capacitance of the pressure-sensor into an equivalent voltage. The effect of change in environmental conditions on the CPS and subsequently upon the output of the SCC is nonlinear in nature. Especially, change in ambient temperature causes response characteristics of the CPS to become highly nonlinear, and complex signal processing may be required to obtain correct readout. The proposed ANN-based scheme incorporates intelligence into the sensor. It is revealed from the simulation studies that this CPS model can provide correct pressure readout within ±1% error (full scale) over a range of temperature variations from -20°C to 70°C. Two ANN schemes, direct modeling and inverse modeling of a CPS, are reported. The former modeling technique enables an estimate of the nonlinear sensor characteristics, whereas the latter technique estimates the applied pressure which is used for direct digital readout. When there is a change in ambient temperature, the ANN automatically compensates for this change based on the distributive information stored in its weights     

Residual stress evaluation in composites using a modified layer removal method

The layer removal method is often used for measurement of internal stresses in homogeneous polymeric materials. In order to extend the use of this method to laminated composites certain refinements are needed. These include: (i) use of varying material properties (elastic moduli) through the thickness of the composite plate; (ii) use of geometric non-linear analysis to account for large deformations; and (iii) measurement not only of curvatures but also of strains. These refinements are necessary because a non-symmetric laminate is created when layers are removed, which shows large curvatures.

The modified layer removal method was theoretically validated on a typical compression-moulded continuous-fibre laminate (PEI/glass) and a typical injection-moulded short-fibre-reinforced laminate (PC/glass). The modified method produced good results and the need to use the modified layer removal analysis is clearly demonstrated.     

Residual stress analysis in weldments

Residual stresses caused by welding may be of the order of the yield strength. This study aims at estimating these residual stresses through a blend of experimental and theoretical approaches. The factors which affect residual stress build up are many, so it is difficult to completely model thermal-elasto-plastic deformation due to welding. To simplify the analysis rotational symmetry in the case of pipes and plane strain assumption in the case of thick weldments are made. These assumptions need not be always true. In the present approach three-dimensional nature of the problem is preserved. It is validated using some standard test problems. The developed method is applied to some practical cases and the results are presented.