Thermal impact study of block folding and face-to-face bonding in 3D IC

In this paper we study the thermal impact of two high impact design/technology choices for 3D ICs, i.e., block folding and face-to-face bonding. A recent study shows that block folding and face-to-face improve wirelength, power, and performance, but the impact on thermal issue is not studied. Based on commercial-quality 3D IC layouts of large-scale OpenSPARC T2 designs and a highly accurate GDSII-level thermal analysis flow, our results first show that block folding, despite its power density increase, does not worsen thermal issues because of additional TSVs that act as heat conductors. In addition, face-to-face bonding, despite its thermal benefit from the absence of BCB bonding layer and underfill, still does not improve temperature much because of the small F2F via sizes.