#DESIGNCON: "Silicon Interposer Enables 3-D Chip Stack"

Bridging the gap to three-dimensional (3-D) chips can be easier with a silicon interposer to handle the signal redistribution with through-silicon-viass that pack two orders of magnitude more interconnect than traditional planar packaging: R. Colin Johnson @NextGenLog

Rambus' 18-by-18 millimeter silicon interposer (top view) is designed for two die on top side-by-side and one die on the bottom interconnected by double-sided redistribution layers and through-silicon-vias with signal integrity up to 20GHz.
Further Reading