Plastic analysis for through silicon via with actual etching defect of triangular-teeth and scallops

Abstract

Through silicon via (TSV) with triangular-teeth and scalloped side wall (TSSW) not only lowers down the electrical performance but also alters the mechanism of thermal mechanical stability. By considering the realistic etching defects on TSV side wall, a more reasonable and reliable three-dimension (3D) TSV model with TSSW is built. The thermo-mechanical issues induced by the unsmooth side wall of the TSV are studied by finite element method (FEM) in this work. With the presence of TSSW, much more tips in interfaces of the TSV-Cu and SiO2 and the SiO2 and Si are brought and the shear stress and normal stress are distinct comparing with the smooth side wall. Therefore, the thermo-mechanical mechanism of the TSV is changed greatly. By investigating the normal stress, shear stress and strain energy density (SED) of the triangular-teeth local region, it has been found that severe normal stress variation (−200–70MPa) and multiple variation of shear stress τxy contributes the peeling, slip and crack issues. The effective plastic strain, displacement and von Mises stress, and shear stress and normal stress in the X, Y and Z direction are studied in detail. The effect of the TSSW on the thermal stress and keep-out zone (KOZ) size is discussed.