Thermal reliability analysis and optimization of polymer insulating through-silicon-vias (TSVs) for 3D integration

Polymer insulating through-silicon-vias (TSVs) is an attractive approach for high-performance 3D integration systems. To further demonstrate the polymer insulating TSVs, this paper investigates the thermal stability by measuring the leakage current under bias-temperature condition, studies the thermal stress characteristics with Finite Element Analysis (FEA), and tries to improve the thermal mechanical reliability of high-density TSVs array by optimizing the geometry parameters of pitch, liner and redistribution layer (RDL). The electrical measurements show the polymer insulating TSVs can maintain good insulation capability (less than 2×10^-11 A) under challenging bias-temperature conditions of 20 V and 200 C, despite the leakage degradation observation. The FEA results show that the thermal stress is significantly reduced at the sidewall, but highly concentrates at the surface, which is the potential location of mechanical failure. And, the analysis results indicate that the polymer insulating TSVs (diameter of 10 μm, depth of 50 μm) array with a pitch of 20 μm, liner thickness of 1 μm and RDL radius of 9 μm has an optimized thermal-mechanical reliability for application.