Wireless Interconnect using Inductive Coupling in 3D-ICs.

Abstract

The mobile market is growing rapidly, as is the demand for high performance and multiple functions in a single device. 3D integration is a promising solution for integrating heterogeneous ICs in a single device since it can achieve a small form-factor and high performance systems with low power by stacking multiple die vertically and using through-wafer interconnects between the layers. There are several methods proposed to implement vertical links in 3D-ICs. Through Silicon Vias (TSV) are one of the most promising methods because they allow high-bandwidth and high-density interconnect and low power dissipation without increasing silicon area. Another promising method is wireless interconnect using inductive coupling. This has the advantages of not only high data rates and low power, but is compatible with all conventional planar IC processes.

The contribution of this thesis is providing circuit solutions to implement vertical interconnects for 3D-ICs. First, the effect of proximity of TSVs to MOSFETs is characterized, from which guidelines are drawn for circuit design in processes with TSVs. The measurement results show the mobility of an active device changes due to the thermal stress induced by the TSV process. Second, this work characterizes the wireless inductive coupling channel and proposes two circuit techniques to enhance its performance. Resonant Inductive Coupling (RIC) can improve the efficiency of inductive data and power links. Furthermore, the combination of in-phase RIC and regenerative oscillation is shown to effectively boost the received signals in multi-layer stacking. Two prototypes are fabricated to demonstrate inductive data links, and one prototype is fabricated of an inductive power link.