Multiwafer vertical interconnects for three-dimensional integrated circuits

Low-loss multiwafer vertical interconnects appropriate for a microstrip-based circuit architecture are proposed. These transitions have been designed, fabricated, and measured for 100-mum-thick silicon and GaAs substrates separately. Experimental results show excellent performance up to 20 GHz, with extremely low insertion loss (better than 0.12 and 0.38 dB for the two different silicon designs and 0.2 dB for the GaAs transition), and very good return loss (reflection of better than 12.9 and 17.3 dB for the two silicon designs, respectively, and 13.6 dB for the GaAs design). Using a high-performance transition allows for a more power-efficient interconnect, while it enables denser packaging by stacking the substrates on top of each other, as today's technologies demand