High Speed Signal Transmission using Through-Si Vias and Coplanar Waveguides in a 3D IC Test Structure

High frequency signal transmission through silicon substrates is critical for 3D heterogeneous integration. This paper presented fabrication, testing, and simulation of high-frequency interconnects based on through-silicon vias (TSVs) and coplanar waveguides (CPWs) for stacked 3D integrated circuits (3D ICs). Our simulation results showed that adding ground TSVs can improve signal transmission by 6× at 50GHz. We further investigated signal/ground TSV (1SXG) configurations for high-bandwidth signal transmission links. Scattering parameter measurements of fabricated 1SXG TSV structures for frequencies from 100MHz to 50GHz show low insertion loss (S21 less than −1dB up to 50GHz) and return loss (S11 lower than −15dB). These results indicate that these vertical interconnects exhibit good performance for high speed signal transmission. To understand the RF signal transmission in 3D interconnects, we used full wave electromagnetic simulation to investigate the electromagnetic field distribution associated with the ground TSV placement. We observed that the ground TSVs induced substantial overall field confinement, consistent with the experimental observation of improved signal transmission. Simulations also provided design guidance with respect to the substrate conductivity's impact on EM confinement and signal transmission.