Failure analysis of through-silicon vias in free-standing wafer under thermal-shock test

Through Silicon Vias With Invar Metal Conductor for High-Temperature Applications

“…We also use finite-element (FE) simulations to estimate the stress distribution in Invar-based TSVs and in the surrounding silicon at various temperatures. The stress distribution in an Invar TSVs is compared to the stress distribution in a copperbased TSV structure described in literature [9]. We show that the use of Invar reduces the cracking probability and the carrier mobility drifts in the silicon region surrounding the TSV.…”

“…For large numbers of thermal cycles during the lifetime of TSV structures, this stress accumulation can cause delamination and cohesive crack growth, which can in turn result in failure of the electrical contacts [8,9]. Most electronic devices are exposed to numerous thermal cycles during their operating life for different reasons.…”

“…• C reported for the copper TSV structures [9] is used as reference temperature T r . Tungsten has been proposed [25,26] as a better CTE-matched alternative to copper (tungsten CTE is 4.42 ppm/…”

“…However, the SiO 2 layer has been neglected in the FE model Material Range Constants with related function (temperatures in Kelvins) Invar instantaneous Invar mean *ᾱ 25 since its effect on the simulation results proved to be negligible compared to the effects from the thicker spin-on glass layer. The geometrical parameters of the Invar TSV has been chosen to be as similar as possible to the geometry of a copperbased TSV reference structure whose thermomechanical performance has been studied both numerically and experimentally [9]. However, while the reference copper structure has been characterized between -55…”

“…Comparisons between simulated stress distributions and analysis of cross-sections of TSVs after thermal cycling have shown a strong correlation between cracking and regions with high Figure 4). stress concentrations [9,38]. Figure 5 summarizes the fracture modes that have been identified in TSVs at the interfaces between different materials [9,33,38].…”