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This paper presents the development of a thermal-electrical finite element (FE) model with the objective to analyze failure mechanisms responsible of physical degradation (void, copper silicate formation, etc.) caused by high fluence stress of 90nm copper vias for FinfET devices. Indeed in [1], this physical degradation was interpreted as a main consequence of Joule effect, however their employed model reached too low temperatures to explain the observed physical degradation. In order to confirm this, the steady-state FE model developed in this work computes the temperature increase and distribution caused by high electrical current density flowing through a copper contact, considering non-ideal thermal and electrical interfaces. In addition, a sensitivity analysis is performed as a way to identify critical failure parameters. The temperature response of the model to independent variation of electrical resistivity of studied materials, and interfacial electrical and thermal conductance between the copper contact and its diffusion barrier were obtained. The decrease of interfacial electrical conductance triggers steady-state temperatures over copper and silicate melting points and, in consequence leads to temperature high enough to explain the physical degradation.

This work examines stress-induced leakage current (SILC) in both ultrathin silicon oxynitride and hafnium silicate dielectric layers for future MOS technology nodes. SILC is confirmed to be sense voltage dependent and is observed to have a dependence on bulk oxide traps for both dielectric layers. A possible explanation for the sense voltage dependence is provided. SILC is found to be a greater problem in the HfSiON layers, because of its magnitude relative to the initial current. This results in the leakage current density quickly becoming greater than that for SiON. The SILC is found to have a transient component in the HfSiON layers, indicating the presence of slow electron traps. Finally, the correlation between SILC and drive current reduction is demonstrated. It is concluded that in the high-k layers investigated in this study, SILC seems more of a problem than dielectric breakdown. [ABSTRACT FROM AUTHOR]