Modeling and quantification of conventional and coax-TSVs for RF applications

In this work we modeled and simulated through silicon vias (TSV) in low, medium and high resistivity silicon (LRS, MRS and HRS) for frequencies up to 80 GHz. We then quantified the electromagnetic reliability (EMR) problems caused by conventional TSVs, in which silicon is used entirely as the medium for wave propagation. Our results revealed that using these conventional structures leads to high insertion loss, lack of impedance control, cross-talk and strong EMI. For example, for TSVs having a diameter 40 mum and depth of 200 mum, approximately 30% of the power is lost through a conventional TSV in LRS at about 5 GHz if a SiO₂ thickness of 1 mum is considered. We then proposed three different configurations of TSVs, based on the concept of the coaxial transmission line, namely Coax-TSV (SF), Coax-TSV (MDF) and Coax-TSV (LDF) to overcome all the limitations of conventional TSVs. This enables LRS to be used for the development of low-cost silicon-based system modules.