Optimization of the return current paths of interposer TSVs for frequencies up to 110GHz

Silicon interposer technology with through-silicon-vias will play a significant role in the development of future 2.5D systems. Furthermore, such systems will have high density and real-time computing requirements, leading to smaller sizes and higher bit-rates. In this paper, through-silicon-via structures in normal resistivity silicon with 3 different return current configurations are modeled and measured. It is shown that reflections and attenuations in the transmission structure can be predicted and reduced with predictive modeling using full-wave simulation techniques. With a silicon conductivity of 25 S/m, the examined TSV structures enter the quasi-TEM mode between 10GHz and 20GHz with a transmission coefficient of ca. -3dB. The transmission coefficient decreases between -5dB and -7dB, depending on the design of the structure. Reflection coefficients for all three structures reaches a maximum of -11dB as the structure enters the quasi-TEM mode.