Study On Electro-thermo-mechanical Characteristics Of TSV Interconnectors And GaN Field Effect Transistors Applied For Advanced 3D-ICs

During the past decades, the advents and applications of many new technologies, new structures, and new materials have driven the semiconductor technology continually forward. The progress of key TSV technology in 3D Integration Ciruits (ICs) and GaN material has attracted much attention due to their excellent merits. However, there are still many serious challenges that need to be solved concerning their applications. Especially, as the best interconnect solution of 3D integration, the equivalent circuit model of TSV is very important for estimating the performance of TSV interconnects. Moreover, there are many cases of periodic EMP injections in TSV applications where the induced electro-thermo-mechanical responses in TSVs will threaten the regular work and cause reliability problems for ICs. Meanwhile, the physics parameters of TSV materials will become temperature-dependent, which may result in much more complicated fields-coupling responses. As to the high power transistors based on GaN, the Joule heat form the transistors gate will also cause many reliability problems for multi-physics couplings.The thesis is to study the electro-thermo-mechanical problems for the applications of TSV and GaN structures, based on the knowledge of semiconductors, electric circuits, heat conductions, and dynamics and the combination with analytical and numerical methods.First, the thesis is to analytically deduce the capacitance of a single TSV with the effects of applied voltages and ambient temperatures considered. Methods of equivalent circuits will be used to extract the capacitances and conductances of TSV arrays. Partial-Element Equivalent-Circuit (PEEC) and methods of the equivalent circuits will be used to extract the temperature-dependent and frequency-dependent circuit parameters of TSV arrays, including resistance, inductance, capacitance and conductance. At the same time, characteristic impedance and insertion loss of TSV arrays have been studied based on the extracted circuit parameters, which are validated with the numerical results of the commercial software.Second, using the developed finite element method (FEM), the thesis will bring out a revised electro-thermo-mechanical coupling algorithm from the coupling mechanism between electrical field, temperature field and stress field. This algorithm can solve the multi-physics responses fast and accurately, considering the temperature-dependences of material parameters. These parameters include electrical conductivity, thermal conductivity, Young's modulus, and Coefficient of Thermal Expansion (CTE). This dissertation systematically studies the transient electro-thermo-mechanical responses of single-and multi-layer TSVs, and TSV arrays. The factors affecting multi-physics responses are analyzed in detail, including the waveform of EMPs, TSV materials and its geometry parameters.Moreover, this thesis also uses the developed multi-physics TD-FEM algorithm to validate the electro-thermal results of a typical GaN-FET model obtained with the commercial software ANSYS without considering the temperature-depedendence of material parameters. The steady-state responses of the GaN-FET model with temperature-dependent material parameters have been calculated. The transient electro-thermo-mechanical responses of the GaN-FET model have been simulated under the human body ESD, periodic EMP and double-exponent EMP.At last, this thesis studies the thermal resistances and average power handling capabilities of TSV and GaN-FET models with both the analytical method and our developed TD-FEM. The analytical method can only be used to solve the thermal resistance of regular and simple structures and the results agree well with our TD-FEM results.