Thermal-aware Power Network Design for IR Drop Reduction in 3D ICs

Due to the high integration on vertical stacked layers, power/ground network design becomes one of the critical challenges in 3D IC design. With the leakage-thermal dependency, the increasing on-chip temperature in 3D designs has serious impact on IR drop due to the increased wire resistance and increased leakage current. Power/ground (P/G) TSVs can help to relieve the IR drop violation by vertically connecting the on-chip P/G networks on different layers. However, most previous work only fulfills a margin of the full potential of PG TSVs planning since the P/G grids are restricted in a uniform topology. Besides, the overlook of resistance variation and leakage current will make the results less accurate. In this paper, we present an efficient thermal-aware P/G TSVs planning algorithm based on a sensitivity model with temperature-dependent leakage current considered. The proposed method can overcome the limitation of uniform P/G grid topology and make full use of P/G TSVs planning for the optimization of P/G network by allowing short wires to connect the P/G TSVs to P/G grids in non-uniform topology. Moreover, with resistance variation and increased leakage current caused by high temperature in 3D ICs, more accurate result can be obtained. Both the theoretical analysis and experimental results show the efficiency of our approach. Results show that neglecting thermal impacts on power delivery can underestimate IR drop by about 11%. To relieve the severe IR drop violation, 51.8% more P/G TSVs are needed than the cases without thermal impacts considered. Results also show that our P/G TSV planning based on the sensitivity model can reduce max IR drop by 42.3% and reduce the number of violated nodes by 82.4%.