3-D system integration of processor and multi-stacked SRAMs using inductive-coupling link

This paper describes a three-dimensional (3-D) system integration of a full-fledged processor chip and two memory chips using inductive coupling. To attain a 3-D communication link with a smaller area and lower power-consumption, shortening the link distance and preventing signal degradation due to unused inductors are important challenges. Therefore, we developed a new 3D-integrated wire-penetrated multi-layer structure for a shorter link distance and an open-skipped-inductor scheme for suppressing signal degradation. In addition, to avoid undefined-value propagation in stacking multi-memories using an inductive-coupling link, we proposed a memory-access-control scheme with a pinpoint-data-capture scheme. We demonstrate that three fabricated chips can be successfully AC-coupled using inductive coupling. The power and area efficiency of the link are 1 pJ/b and 0.15 mm² /Gbps, respectively, which are the same as those of two-chip integration.