Thermo-Mechanical Reliability of 3D-integrated Microstructures in Stacked Silicon

Abstract

This paper investigates the thermo-mechanical reliability of inter-chip-vias (ICV) for 3D chip stacking after processing and under external thermal loads relevant for the envisaged field of application (mobile, automotive) by Finite Element simulation. First the materials are characterised by nano-indentation to determine elasto-plastic data. Finite Element simulations are used to reproduce these data and to extract local material properties like E-modulus and yield stress. Accumulated plastic strain is used as failure indicator under periodic thermal loading of an ICV. Geometrical, material and process-related parameters are varied to obtain first design guidelines for this new technology. The locations of stress and strain accumulation are given.

Thermo-mechanical reliability of 3-D ICs containing through silicon vias

“…Various approaches were taken in the past to address these reliability issues. For example, FEA was performed to determine the stresses developed during the manufacturing process [5,6], and various via filling designs [7,8] were proposed to minimize the thermal stresses generated by the TSVs.…”

Wafer‐Level 3D System Integration

“…The whole process, including calibration [36], is outlined in Reference [37]. By this method, values of E ¼ 93 GPa, s y ¼ 190 MPa and M ¼ 1400 MPa were obtained for the AlSiCu layer.…”

“…By this method, values of E ¼ 93 GPa, s y ¼ 190 MPa and M ¼ 1400 MPa were obtained for the AlSiCu layer. For the remaining material data please refer to Table 16.1 or Reference [37]. …”

“…The latter is necessary to capture the correct stresses evolving at bi-material interfaces due to thermal mismatch on cooling from the respective process temperature. Figure 16.27 shows the thermal load history according to the different thermal process steps like, for example, layer deposition, etching or structuring [37], starting from the thermal oxide formation on the wafer. 1.…”

“…Here, the most important results of the FE-simulations [37] are depicted for equivalent stress and equivalent plastic strain, where always the maximum value at the most critical location is given after all process and thermal cycling steps. As the magnitude of stress or plastic strain can be taken as a failure criterion, design optimization involves their possible reduction.…”