Moore’s law has remarkably promoted the development of semiconductor technology over the last decades. The advanced packaging involving novel materials, structures, and processes has contributed significantly to achieving excellent performance. Among various forms of advanced packaging, wafer-level-fan-out packaging is superior to standard wafer-level packaging in that it allows more input/output (I/O) connections, leading to landmark development for high-end devices. Furthermore, fan-out wafer-level package (FOWLP) technology enables heterogeneous integration of chiplets fabricated with different manufacturing processes, which provides integrated, sophisticated, and multifunctional dies with higher performance, lower cost, and tinier size. In packaging materials, processes, and structures, a thorough understanding of the process mechanics is necessary to ensure accuracy, while multiphysical field and multiscale modeling are beneficial to clarifying the internal mechanism of warpage. Process mechanics was applied to FOWLP and the characteristics were systematically expounded. Focusing on the warpage analysis of the embedded silicon fan-out (FO) wafer-level package, we introduced the principle of process mechanics and explored the material–structure–process interaction. The typical processes (including: 1) cleaning and litho cavity; 2) die attach and assignment; 3) dry film and dielectric layer 1 and patterning; 4) physical vapor deposition (PVD) seed layer 1 and patterning copper plating and redistribution layer (RDL) 1; 5) dielectric layer 2 and patterning; 6) PVD seed layer 2 and patterning copper plating and RDL 2; and 7) passivation layer, drop ball back grinding, and dicing) of the embedded silicon FO packaging are analyzed in detail to explore the warping evolution of individual processes. In addition, a material equivalent model of representative volume element (RVE) and an extended theoretical model of a multilayer structure were proposed. The comprehensive comparison for the extended theoretical model, experimental measurement, and finite element model (FEM) showed that the theoretical model is effective and relatively accurate. Overall, both the theoretical model and FEM are feasible approaches for predicting the warpage during the manufacturing process.

Optically clear adhesive (OCA) has been widely used in flexible devices, where wavy stripes that cause troublesome long-term reliability problems often occur. The complex mechanical behavior of OCA should be studied, as it is related to the aforementioned problems. Therefore, it is necessary to establish reasonable mechanical constitutive models for deformation and stress control. In this work, hyperelastic and viscoelastic mechanical tests were carried out systematically and relative constitutive models of OCA material were established. We found that temperature has a great influence on OCA’s mechanical properties. The stress and modulus both decreased rapidly as the temperature increased. In the static viscoelasticity test, the initial stress at 85 °C was only 12.6 kPa, 57.4% lower than the initial stress at 30 °C. However, in the dynamic test, the storage modulus monotonically decreased from 1666.3 MPa to 0.6628 MPa as the temperature rose, and the decline rate reached the maximum near the glass transition temperature (T_g = 0 °C). The test data and constitutive models can be used as design references in the manufacturing process, as well as for product reliability evaluation.

With the drastic reduction of the TSV diameter leading to a critical dimension comparable to the Cu-filled grain size, the grain condition strongly influences the thermo-mechanical behavior of the TSV. In this work, the TSV-Cu cross-section with different grain sizes is characterized by EBSD, confirming that the sidewall grain size (0.638–1.580 μm) is smaller compared to other regions (1.022–2.134 μm). A finite element model (FEM) considering copper grains is constructed by using Voronoi diagrams to investigate the effect of sidewall grain size as well as area on the thermo-mechanical behavior during annealing. The material parameters in the FEM are optimized through nanoindentation inversion and considering the mechanical property anisotropy of copper grains. The yield strength σ_y and hardening exponent n of TSV-Cu are 74.6 MPa and 0.514. The simulation results indicate that the protrusion of TSV-Cu after annealing tends to increase initially and then decrease with smaller sidewall grain size and area. The maximum increase in protrusion caused by the two variables can reach 6.74% and 14.6%, respectively, relative to the average grain condition. Additionally, the simulation results were validated by quantifying grain boundaries in TSV-Cu samples with varying grain sizes.

With the rapid development of 3D packaging technology, the thermal reliability of high-aspect-ratio TSV has become an urgent problem. The inhomogeneity of TSV-Cu induced by the grain growth during annealing should not be ignored. The inhomo-geneities in grain size, morphology, and mechanical property anisotropy, among others, may severely affect TSV manufacturing. In this work, the characterization experiments have been carried out by SEM and EBSD on TSV samples with an Aspect-Ratio of 10 firstly, then the copper grain was grown into morphologies by DFM, and a variety of models with different TSV-Cu grain sizes and distributions were built considering the mechanical anisotropy of Cu crystal. To explore the influence of the distribution of TSV-Cu anisotropic grains on their thermo-mechanical reliability at high temperatures and protrusion behavior after annealing, a group of annealing processes with different temperatures was simulated. The results show that TSV-Cu with larger grains in the top region has lower high-temperature thermal stress, equivalent plastic strain and residual stress after high-temperature annealing. However, the protrusion height is only related to average grain size, and the TSV-Cu filled with large-size grain has the largest protrusion height and is more prone to failure.

Through silicon via (TSV) is a core technology in 3D integration. Interface failure is one of the most noted failure forms of TSV. The barrier layer Ta, which is between the media Cu and the insulating layer SiO2, is often neglected due to its small thickness. However, the Cu/Ta interface is prone to cracking and debonding, thus plays an important role in TSV interface reliability. In this work, the Cu/Ta interface models with different structures were established by molecular dynamics simulation method. Then tensile simulations were performed. The effects of interface structures on the interface mechanical properties and the deformation mechanisms were analyzed based on dislocations and crystal phase transitions. The critical strain energy release rate values of the rough and tilted interface were 17.21 J/m2 and 13.66 J/m2, respectively. Both of them were larger than the perfect interface, whose value was 11.24 J/m2. While the interface void decreased the energy release rate significantly. When the void length increased from 4 to 16 nm, the energy release rate decreased almost monotonously from 6.06 to 1.46 J/m2. The Ta layer was more stable compared with the Cu layer. During the tensile process, dislocation reactions, phase transitions and stress concentrations mainly occurred in the Cu layer. The cracks sprouted on the Cu layer and extended along the interface. The local plastic deformation of Cu layer around the void was the main factor affecting the tensile deformation behavior. The longer the void, the greater the local plastic deformation.