Thermomechanical reliability of a Cu-TSV integration model based on 3D fabrication processes

Abstract

In the 3D integration stages, the structure of the TSV is changed with the development of the procedure. The 3D though silicon via (TSV) integration models with the new updated structure depended on the integration processes (fabricating redistribution layer (RDL), reflowing solders and filling underfill) were analytically studied in this work. The equivalent stress, von Mises stress, was used to describe and evaluate the change rule and trend of the 3D TSV integration models during the integration integrations. The changing mechanism of thermal stress and strain on the updated models was varied for the free-form deformation space was substituted by the new fabricating structure. The thermal mechanical stability of the updated 3D TSV integration model is analyzed by the steady-state solver finite element method (FEM). The maximal von Mises stress of the updated models decreased with the procedures carried on. The thermal mechanical reliability of final 3D TSV integration model during the operating stage was simulated by the time-dependent solver of FEM. After 3 cycles the maximal thermal stress and strain at the maximal temperature (MT) dropped to near the yield stress of Cu, nevertheless, in the 6 cycles the maximum of the MT raised up but still less than the maximum of the past three cycles may result from the reshaped structure and strain harness processes. The tearing and cracks might be induced for the tensile stress in both X and Y directions are all enlarged greatly. However, the shear stress got into a stable value about 105 MPa after 2 cycles.