Analysis and mitigation of lateral thermal blockage effect of through-silicon-via in 3D IC designs

The three-dimensional integrated circuits (3D ICs) offer performance advantages thanks to the increased bandwidth and reduced wire-length enabled by through-silicon-via structures (TSVs). Traditionally TSVs have been considered to improve the thermal conductivity in the vertical direction. However, the lateral thermal blockage effect becomes increasingly important for TSV via farms (a cluster of TSV vias used for signal bus connections between layers). TSV farms can cause different thermal effects on different layers due to the unequal x, y, z thermal conductivities. This can exhibit itself as thermal improvement in the vertical heat flow, at the same time lateral heat blockage effects in thinned pass-through layers. In this paper, we propose a thermal-aware via farm placement technique for 3D ICs to minimize lateral heat blockages caused by dense signal bus TSV structures. By incorporating thermal conductivity profile of via farm blocks in the design flow and enabling placement/aspect ratio optimization, the corresponding hotspots can be minimized within the wire-length and area constraints.