Pumping and shrinking deformation of TSV-Cu under thermal cycling loads: A cross-scale analysis approach

Abstract

Three-dimensional (3D) integrated packaging represents a novel generation of semiconductor packaging technology, with through-silicon via (TSV) being the most critical structure. However, its failure mechanism and reliability evaluation issues remain inadequately addressed. The thermal mismatch at the TSV microstructure interfaces generates substantial thermal stresses under thermal cycling loads, leading to pump and shrinkage deformation in the filled copper and adversely impacting the structural reliability and performance. This study presents a cross-scale analysis method that integrates the principles of crystal plasticity (CP) with the finite element method (FEM) while taking thermal expansion effects into account. Utilizing this method, the pump and shrinkage phenomena of seven common textures of TSV electroplated copper (TSV-Cu) crystals under thermal cycling load were compared, and the distribution of equivalent stress, elastic strain, and plastic strain were analyzed. Subsequently, the effects of TSV-Cu grain number, topological morphology, random orientation, orientation dispersion, grain size, and orientation mismatch at the top of TSV on deformation were investigated. Furthermore, the residual stress and deformation associated with TSV pumping and shrinking under thermal cycling were analyzed. The conclusions drawn from the cross-scale analysis method proposed in this study are consistent with the experimental observations and analyses reported in the relevant literature, thereby validating the method's accuracy. The research findings indicate that when the copper filler exhibits a Cube texture, the stress, strain, and deformation are relatively minimal. In the absence of a preferred orientation in the copper filler, the dispersion of copper expansion and contraction deformation is dependent on the grain size, and the deformation follows a Weibull competitive distribution. The topological morphology of the grains induces non-uniform deformation in the structure, resulting in localized and annular deformation patterns. The grain size and orientation mismatch at the top of the TSV-Cu significantly influence the pump and shrinkage deformation of copper under thermal cycling conditions. Finally, the study concludes with recommendations for structural process optimization. By linking grain microstructure evolution to macroscopic boundaries and loads through the cross-scale analysis method, this research provides insights into the microscopic-scale pump and shrinkage phenomena of TSV-filled copper under thermal cycling, offering valuable references for TSV structural design, process optimization, failure analysis, and life assessment.