Theanalysis Of TSV-Cu’s Properties Based On Nanoindentation And Finite Element Simulation

In modern microelectronic industries, the3D packaging is potential solution tomeet the demands of feature size reduction and increased transistor performance forconsumer electronic devices. Meanwhile, it is considered to be the mainstream of thedevelopment direction of future packaging technology. Through-Silicon-Via (TSV),providing short vertical interconnects and high I/O counts, is regard as the core of3Dintegration.TSV is by making through hole in the vertical direction on a silicon wafer, thenfilling a conductive material inside the hole to achieve the interconnection betweendifferent chips. Copper (TSV-Cu) has usually been chosen to fill the TSV byelectroplating because of its high conductivity, mature electro-deposition process andhigh electro-migration resistance.The present thesis pays attention to study the mechanical properties for TSV-Cubased on nanoindentation tests and finite element simulation. To obtain theelastic-plastic properties of TSV-Cu, nanoindentation tests are conducted. WithOliver-Pharr algorithm and the continuous stiffness measurement method, themeasured elastic modulus and hardness of the TSV-Cu are155.47GPa and2.47GPa,respectively. An FEM simulation method is adopted for reverse analysis ofnanoindentation loading process, then, the representative stress and representativestrain of TSV-Cu are determined by comparing the maximum value of simulated loadto that of experimental load. The strain hardening exponent determined bydimensionless functions is0.4892. The yield stress acquired by substituting therepresentative stress, the representative strain and the strain hardening exponent intothe power law constitution is47.91MPa. Finally, the power law elastic-plasticstress-strain relationship of TSV-Cu is obtained. TSV contains Cu/Ta/SiO2/Simulti-layer interface after filling. The mechanical performance of TSV-Cu is affectedby the surrounding effect of TSV multi-layer interface and its micro-structure. Thusthe mechanical behavior of TSV-Cu is apparently different from the macro Cu.This research has great significance on the further study of the micro-structure ofTSV-Cu, as well as on the reliability and design of TSV structures.