Abstract
Traditional metrology has been unable to adequately address the reliability needs of emerging integrated circuits at the nano scale; thus, new metrology and techniques are needed. In this paper, we use microwave propagation characteristics (insertion loss and dispersion) to study the atmospheric interconnect corrosion under accelerated stress conditions. The results presented in this work indicate that the corrosion resilience of the test device is limited by the thermal aging of the passivation layer.
Highlights
The reliability challenges of emerging advanced integrated circuits nodes have not been adequately addressed at the nano-scale level by traditional metrology.[1,2] For example, the stress buildup, due to thermal mismatch of the materials of construction, results in the generation of performance limiting defects,[3] which are not readily detected with such techniques as direct current (DC)-resistance changes
Physical analyses of devices that failed while in use suggest that damage in final encapsulation materials is a significant failure mode, probably due to the fact that the stresses in interconnects are influenced by the intrinsic properties of the passivation dielectrics.[4,5]
We have demonstrated that broadband microwave-based techniques afford detailed insights into the thermomechanical reliability issues,[20,16,21,22] as well as to probe the impact of temperature and current on the pre-failure, in the early stages of EM of Cu through silicon via (TSV)-based interconnects in 3D-ICs.[23]
Summary
The reliability challenges of emerging advanced integrated circuits nodes have not been adequately addressed at the nano-scale level by traditional metrology.[1,2] For example, the stress buildup, due to thermal mismatch of the materials of construction, results in the generation of performance limiting defects,[3] which are not readily detected with such techniques as DC-resistance changes. Such transitions show up in the insertion loss (S21) spectra and can be modeled with lumped-RLGC equivalent circuits.[18,19] For integrated circuits on silicon substrates, simulations indicate that while isolation dielectric issues dominate low frequency (10 to 300 MHz) behavior, the resistance of the silicon substrate dominate 300 MHz-1 GHz region, and the capacitance of the silicon dominates the high frequency (> 1 GHz) region of the microwave spectrum as observed by increased insertion loss behavior, respectively.[18] We have demonstrated that broadband microwave-based techniques afford detailed insights into the thermomechanical reliability issues,[20,16,21,22] as well as to probe the impact of temperature and current on the pre-failure, in the early stages of EM of Cu through silicon via (TSV)-based interconnects in 3D-ICs.[23] Both electromigration (EM) and corrosion failure modes manifest in increased interconnect direct current resistance (RDC); so, techniques are needed to distinguish between them.[20,24] In this paper we characterize heat-induced atmospheric corrosion of metal interconnects, due to the failure of the encapsulating material, and attempt to distinguish it from other preelectromigration (pre-EM) processes that occur during the latent period before catastrophic EM failure as described by Gousseau et al.[25]
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