Design Methodologies for Low-Power 3-D ICs with Advanced Tier Partitioning

Low power is considered as the driving force for 3-D ICs, yet there have been few thorough design studies on how to reduce power in 3-D ICs. In this paper, we discuss computer-aided design techniques and design methodologies to reduce power consumption in 3-D IC designs using a commercial grade CPU core (OpenSPARC T2 core). To demonstrate power benefits in 3-D ICs, four design techniques are explored: 1) 3-D floorplanning; 2) metal layer usage control for intrablock-level routing; 3) dual-Vth design; and 4) functional unit block (FUB) folding. The benefits and challenges of multiple FUB folding are also discussed. Finally, the through-silicon via technology scaling impact on FUB folding and 3-D power benefit is examined. With the aforementioned methods combined, our 2-tier 3-D designs provide up to 52.3% reduced footprint, 27.9% shorter wirelength, 35.4% decreased buffer cell count, and 27.8% power reduction over the 2-D counterpart under the same performance.