Air-gap-based RF coaxial TSV and its characteristic analysis

Many 3D IC applications such as MEMS and RF systems require Through-Silicon Via (TSV) with operations for high-speed vertical communication. In this paper, we introduce a novel air-gap coaxial TSV that is suiTab. for such RF applications. Firstly, the detailed fabrication process is described to explain how to acquire such a structure. Then, an Resistor Inductance Conductance Capacitance (RLGC) model is developed to profile the transverse electromagnetic field effect of the proposed air-gap TSV. The model is further verified by a 3D field solver program through the S-parameter comparison. With reference to the numerically simulated results, this analytical model delivers a maximum deviation of less than 6&. on the conditions of varying diameters, outer to inner radius ratios, and SU-8 central angles, etc. Taking advantages of scalability of the model, a number of air-gap-based TSV designs are simulated, providing 1.6～4.0 times higher bandwidth than the conventional coaxial TSVs and leading to an efficient high frequency vertical RF interconnection solution for 3D ICs.