Structural integrity optimization of 3D TSV package by analyzing crack behavior at TSV and BEOL

Abstract

New electronic devices with small size and low power consumption are in demand in recent years. Miniaturization and complex product are required in modern electronics for more functionality in the smaller electronic package. To overcome such issues, 3D packages or package on package (PoP) are introduced. The 3D packaging is stacking of chip on top of another which is emerging as a powerful technology that satisfies such integrated circuit (IC) package demands. A 3D package using through silicon vias (TSVs) has emerged as an effective technology for future interconnection requirements. The mismatch of coefficient of thermal expansion (CTE) of the SiO2 and copper used in TSV can induce a lot of thermal stresses. The stress developed at interfaces results in the interfacial delamination of TSV, which is mainly driven by a shear stress concentration at the point. The developed thermal stresses are critical for the thermo-mechanical reliability of the 3D package. In this paper, the effect of package structure on the failure metric of the 3D package has been studied. J-integral has been used to quantify the crack driving force. The crack is modeled at the TSV and BEOL (Back End of the Line) and the die-substrate thickness is varied and studied during chip attachment process and under thermal cycling load for optimizing the die and substrate thickness design [1]. Finite Element method have been used to analyze the thermo-mechanical stresses and fracture parameters in TSV structures 3D package. For this study, full field compact modeling methodology [2] has been leveraged for the ease of FEA using ANSYS Workbench 17.2. An optimized package assembly was obtained to reduce the crack driving energy at the TSV region and in the BEOL dielectric layer. A design approach has been proposed to mitigate brittle failure issues thus improving the thermo-mechanical reliability of the 3D package.