铝硅合金互连线电迁移失效试验

随着微电子技术的发展,作为超大规模集成电路互连线的金属薄膜的截面积越来越小,其承受的电流密度急剧增加,电迁移引起的互连失效变得尤为突出.针对集成电路中金属互连线的电迁移现象,以Black方程为基础,对其进行了修正.并以铝硅合金互连线为研究对象,对其电迁移过程进行了详细的加速寿命试验研究,获取了修正后的Black方程中的相关参数,分析了不同环境温度、不同电流密度、不同初始电阻等因素对铝互连线电迁移的影响规律.结果表明,铝硅合金互连线的电迁移寿命与上述参数均成反比关系.     

Packaging for optoelectronic interconnections

If optoelectronics are to be widely applied in consumer products as well as specialized technologies, the cost of packaging the components must be kept down. Until recently, the specialized nature of optoelectronics applications meant that packaging was mainly an afterthought. Today, it is becoming a vital part of the overall device planning and manufacturing process. This article describes some of the technologies and costs associated with optoelectronic device packaging.     

Electromigration effects upon interfacial reactions

At the joints in microelectronic products, electric currents pass through interfaces of dissimilar materials. At these joints, atomic fluxes are driven by both the compositional gradients and electromigration effects. Although interfacial reactions at these joints appear to be affected by both of the driving forces, most often only compositional gradients are investigated when interfacial reactions are concerned. This study examines the effects of electromigration upon interfacial reactions together with the effects of compositional gradients, primarily in lead-free solder joints. It is found that electromigration significantly affects intermetallic compound growth in various systems. Growth rates of the intermetallic compounds are either enhanced or retarded depending upon the diffusion directions of the primary moving species and those of the applied electric currents. This study demonstrates that electromigration effect is an important factor in the interfacial reactions at the joints with the passage of electric currents. For more information, contact Sinn-wen Chen, National Tsing Hua University, Department of Chemical Engineering, Hsin-Chu, Taiwan 300, ROC;+886-3-572-1734; fax +886-3-571-5408; e-mail swchen@che.nthu.edu.tw.     

金属互连结构的电迁移仿真分析

针对集成电路中金属互连线的电迁移现象,应用有限元分析软件ABAQUS,对铝硅合金互连线的电迁移过程进行了电热耦合研究,分析了不同电流密度与电势梯度、热通量、互连线内部总能量之间的相互关系,比较了不同结构尺寸对铝互连线电迁移失效的影响规律.结果表明,在互连线的狭窄部位,电势梯度和热通量达到最大值并具有集中性;电势梯度和热通量与通电时间及电流密度均成正比例关系;随着通电时间的延长,互连线内部总能量的变化趋势为先急剧下降再上升并达到某一平衡值;随着铝互连线宽度的增加,互连线内部的热通量逐渐减小.对于文中分析的结构模型,当互连线宽度低于2μm后,互连线失效的概率将大幅度增加.     

无铅电子封装中的电迁移

随着电子产品向微型化、多功能化的发展,封装焊点尺寸逐渐减小,电流密度急剧增大,由电迁移引起的焊点失效问题也日趋严重。电迁移使焊点的阳极产生凸起、挤出、晶须,甚至产生塑性变形,阴极产生空洞、裂纹,降低焊点的可靠性,导致电路短路或者断路,使元器件快速失效。本文介绍了近期国内外有关Sn-Cu,Sn-Ag,Sn-Ag-Cu,Sn-Zn及Sn-Bi等无铅钎料电迁移现象的研究进展,并分析、评述了电迁移对无铅钎料焊点可靠性的影响机制。     

Electromigration in solder joints and solder lines

Electromigration may affect the reliability of flip-chip solder joints. Eutectic solder is a two-phase alloy, so its electromigration behavior is different from that in aluminum or copper interconnects. In addition, a flipchip solder joint has a built-in currentcrowding configuration to enhance electromigration failure. To better understand electromigration in SnPb and lead-free solder alloys, the authors prepared solder lines in v-grooves etched on Si (001). This article discusses the results of those tests and compares the electromigration failure modes of eutectic SnPb and SnAgCu flip-chip solder joints along with the mean-timeto-failure.     

Future manufacturing techniques for stacked MCM interconnections

As multichip modules (MCMs) grow in chip count and complexity, increasingly large numbers of input/output (I/O) channels will be required for connection to other MCMs or printed wiring boards. In applications such as digital signal processing, large increases in processing density (number of operations in a given volume) can be obtained in stacked MCM arrangements. The potential pin counts and required I/O densities in these stacked architectures will push beyond the limits of present interlevel coupling techniques. This problem is particularly acute if easy separation of layers is needed to meet MCM testing and yield requirements. Solutions to this problem include the use of laser-drilled, metal-filled electrical vias in the MCM substrate and also optoelectronic data channels that operate in large arrays. These arrays will emit and detect signals traveling perpendicular to the surface of the MCM. All of these approaches will require packaging and alignment that makes use of advanced MCM manufacturing techniques.     

熔融状态下共晶SnBi钎料的电迁移特性

研究电流密度为1.5×104 A/cm2时,共晶SnBi焊点的微观组织的演变.试验过程中应用Microview MVC2000图像采集卡对焊点形态的变化进行实时监控.通电仅110 s,焊点的局部区域开始熔化;130 s后达到完全熔融的状态.结果表明:通电10 min后,焊点的阳极附近形成了大量的块状Bi相,而在阴极则以细条形的Bi相为主.然而抛光后发现,阴极和阳极的微观组织保持一致,钎料基体内出现了大量的Bi的小颗粒形成的聚集,阴极界面出现了空洞.通电30 min后,共晶组织的均匀分布已经被打乱.阳极附近出现了Bi的聚集,而且阳极界面的IMC层比阴极界面的IMC层厚.     

电迁移诱发镀层锡须生长行为分析

分析了0.3×104 A/cm2恒定电流密度和四种不同加载时间（0,48,144和240 h）电迁移条件对6.5 μm厚镀锡层表面锡须生长行为的影响,以及不同电流密度对阴极裂纹宽度的影响.结果表明,电迁移加速了镀层表面锡须的形成与生长,随着电迁移时间的延长,锡须长度不断增加.此外,电迁移导致在阴极首先出现了圆形空洞,随后在两极均形成了圆形空洞,并且在阴极处还发现有微裂纹存在,随着电流密度增加,阴极裂纹宽度也随之增加,电流密度为0.5×104 A/cm2时,平均最大裂纹宽度约为9.2 μm.     

Electromigration and the electroplastic effect in aluminum SiC MMCs

Aluminum SiC metal-matrix composites fabricated by standard powder-metallurgy compaction and sintering were subjected to high-density alternating-current pulses during transverse rupture testing. Results indicate increased strength due to electromigration. Decreases in flow stress were observed during plastic deformation and were attributed to the electroplastic effect. For more information, contact J.A. Rice, Marquette University, 1515 W. Wisconsin Avenue, Milwaukee, Wisconsin 53201-1881; (414) 288-5405 (414) 288-7790 James.Rice@marquette.edu.     

Electromigration of Pb-free solder under a low level of current density

In this study, current stressing experiments were conducted to investigate electromigration of 99.3Sn0.7Cu solder with Au/Ni UBM in BGA packaging. Although the average current density in the solder bump was only 0.4 × 10⁴ A/cm², the maximum value of the current density was 1.42 × 10⁵ A/cm², which exceeded the threshold value for electromigration to occur. Furthermore, the current caused substantial Joule heating which significantly rose the local temperature of the interconnection. A novel method, forced convection heat-transfer, was introduced to dissipate the Joule heating and cool down the interconnection. Hence, electromigration was achieved under a low level of current density, because the effect of thermal diffusion of atoms was minimized. Ni and Cu migration from the cathode side to the anode side driven by electrons was observed on both the chip and substrate due to the special symmetrical structure. At the low temperature, a few small pieces of intermetallic compound (IMC) were found in the solder bumps, because Ni and Cu diffused into the Sn by a combination interstitial and boundary diffusion. When the temperature approached the melting point of the solder, many large IMC regions appeared along the boundaries in the solder. Here it is believed that Ni and Cu had a high rate of volume diffusion into Sn at the high temperature.     

锌对共晶锡铋合金的电迁移可靠性的影响

本文选取了应用最为广泛的无铅钎料之一的共晶锡铋合金进行研究,对其进行锌的掺杂,以期透彻的了解锌对无铅钎料在电迁移作用下的行为。研究结果显示,在钎焊结束之后,电流加载之前,掺入的锌会通过促进合金晶粒粗化在一定程度上降低焊点的抗拉强度。但是对焊点进行电流密度为104 A/cm2的电流加载100h后,锌的掺入可以避免锡铋合金中锡相与铋相晶粒之间形成缝隙,从而对焊点的可靠性有显著的提升。     

Determination of the quality of resistance welded interconnections in lead-acid batteries

Experimental results are used to justify the method of determination of the quality of resistance welding of samples of interconnections of lead-acid batteries using torsion tests. The original design of the specialized stand is proposed for the tests.     

Cu/Sn-58Bi/Cu焊点电迁移行为研究

采用双辊快速凝固技术制备了Sn-58Bi钎料薄带,并制备Cu/Sn-58Bi/Cu线性焊点。使用电子探针(EPMA)及能谱分析(EDS)研究焊点在电流密度为1×10^4 A/cm^2(25℃)下界面金属间化合物(IMC)、元素扩散与钎料基体组织演变规律。结果表明,随着通电时间延长阳极界面处的IMC层的形状从扇贝状转变为锯齿状,阴极界面处的IMC层由扇贝形变为不规则,其厚度逐渐增加。阳极由于Bi的偏聚形成了富Bi层,Sn在阴极偏聚,基体共晶组织(Bi+β-Sn)粗化。基于线性拟合可知,阳极和阴极的界面IMC层的生长系数n分别为0.263和0.442,其生长机制可归结为体积扩散。     

具有纳米结构的增强颗粒对SnBi焊点电迁移的影响

探究了颗粒增强无铅复合钎料的电迁移特性。试验采用具有纳米结构的笼型硅氧烷齐聚物(POSS)颗粒作为增强颗粒,制备SnBi基复合钎料。在25oC,104A/cm2条件下,对钎料一维焊点实施不同时间的通电试验,并对焊点表面形貌和内部显微组织进行观察。结果表明,相对于共晶SnBi焊点,POSS颗粒增强复合钎料焊点的电迁移现象明显受到抑制。通电336h后,复合钎料焊点表面变化很小,界面处聚集的富Sn和富Bi层厚度很小,表明POSS颗粒能够有效抑制通电焊点中的物质扩散。     

Precision high temperature lead-free solder interconnections by means of high-energy droplet deposition techniques

This paper presents a number of numerical models that illustrate the experimental details of the key physical phenomena affecting the operation of novel materials deposition processes for electronics assembly. These processes include both laser and electric arc based droplet deposition processes. These are being developed in the electronics industry to allow the use of new lead-free alloys as replacements for high temperature lead based alloys, such as Sn5Pb95. The paper presents models of physical processes with respect to the desired process metrics of droplet size and deposition accuracy and reviews the potential limiting product - process interactions such as excessive thermal excursions and their effects on the target materials being joined.