A Hybrid 3D Interconnect With 2x Bandwidth Density Employing Orthogonal Simultaneous Bidirectional Signaling for 3D NoC

For the first time, this work presents a wireless-wireline hybrid 3D interconnect that employs orthogonal simultaneous bidirectional signaling for 3D Network-on-chip to achieve $2\times $ bandwidth density. We combine wireless near-field inductive coupling channel (NFIC) encompassing wireline through-silicon vias (TSV) to leverage orthogonal simultaneous bidirectional (SBD) signaling. This technique provides an efficient way of doubling interconnect bandwidth in the same area by means of passive wireless and wireline interconnects. The proposed hybrid 3D interconnect shows at least -70dB of NFIC-TSV isolation in the band of interest. We also present a comprehensive link analysis to derive the energy-area trade-off of an NFIC link and its fundamental performance limits. Further, we demonstrate on how equalization has the potential to decouple the fundamental energy-area tradeoff. The prototype transceiver measures a simultaneous bidirectional data and clock communication at an effective data rate of 6.6 Gb/s consuming 263 fJ/bit in 65 nm CMOS bulk process. The developed hybrid 3D interconnect architecture exhibits a $2\times $ improved link performance over state-of-the-art 3D simultaneous bidirectional links. A hybrid 3D Network-on-chip (3D NoC) implementation is demonstrated using the proposed hybrid interconnect technology and shows a 50% lower area and cost for the same energy-delay-product (EDP) over the conventional TSV based links.