Morphology of electromigration-induced damage and failure in Al alloy thin film conductors

Distinct morphologies of electromigration-induced voids and failures are shown for Al, Al-2%Cu, and Al-2%Cu-l% Si narrow (1–6 μm) unpassivated thin film conductors. SEM and TEM images typically show large non-fatal voids and narrow slit-like open circuit failures for all film conditions and accelerated test conditions. Evidence for transgran-ular slit failures is shown for 1.33 μm wide conductors. A simple model for void growth is presented which accounts for the void morphologies seen. The observed morphologies and the results of void growth modelling suggest that slit voids nucleate after other voids and rapidly produce failure. These conclusions are discussed in terms of ‘classical’ models for electromigration failure processes and resistance and noise power monitoring techniques.     

Barrier layer effect of tantalum on the electromigration in sputtered copper films on hydrogen silsesguioxane and SiO2

As IC devices scale down to the submicron level, the resistance-capacitance (RC) time delays are the limitation to circuit speed. A solution is to use low dielectric constant materials and low resistivity materials. In this work, the influence of underlying barrier Ta on the electromigration (EM) of Cu on hydrogen silsesquioxane (HSQ) and SiO₂ substrates was investigated. The presence of a Ta barrier not only improves the adhesion between Cu and dielectrics, but also enhances the crystallinity of Cu film and improves the Cu electromigration resistance. The activation energy obtained suggests a grain boundary migration mechanism and the current exponent calculated indicates the Joule heating effect.     

互连铝通孔电迁移特征及其可靠性研究

研究了超大规模集成电路铝互连系统中铝通孔的电迁移失效机理及其可靠性寿命评价技术.试验采用CMOS和BiCMOS两种工艺各3组的铝通孔样品,分别在三个温度、恒定电流的加速条件下试验,以通孔开路为电迁移失效判据,最后得到了在加速条件下互连铝通孔的电迁移寿命,其结果符合标准的威布尔分布,试验准确可行.通过电迁移模型对试验数据进行了拟合,得到了激活能、电流加速因子和温度加速因子,计算出了正常工作条件下通孔电迁移的寿命,完成了对铝通孔电迁移的研究和寿命评价.