Transmission Characteristics of Long-Chain Through Silicon Via-Redistribution Layer Interconnects

Current research on the transmission characteristics of through silicon via-redistribution layer (TSV-RDL) interconnects is basically limited to the single-pair interconnect (a device with two TSVs connected by an RDL line is referred to as one-pair), which is obviously insufficient for highly integrated 3-D packaging. Thus, this article aims to simulate the actual long-chain interconnects by establishing an equivalent circuit model of multipair TSV-RDL interconnects in order to explore their transmission characteristics. First, the equivalent circuit model of long-chain ground-signal-ground type (GSG-type) TSV-RDL interconnects is established based on the correlation between single-pair and multipair interconnects. Second, the transmission performance of long-chain interconnects is investigated by analyzing the reasons for the differences in insertion loss of various length test vehicles in the frequency band from 0.01 to 40 GHz. Compared to RDL lines, TSVs have a greater impact on the overall loss. The resistance of interconnects and the capacitance of the insulating layer at low frequency, the capacitance and conductance associated with the conductive substrate in the mid-frequency range, as well as the inductance in the high-frequency region all play pivotal roles in impedance changes in their respective domains. Finally, the above analysis points out the optimization of the long-chain interconnect by increasing its length while avoiding excessive inductance due to RDL lines in order to reduce the use of TSVs and thus improve the overall transmission performance.