Efficient Backside Power Delivery for High-Performance Computing Systems

In this work, we present a thin-profile, efficient power delivery approach, including a voltage regulator with in-package power inductor and backside power delivery network (PDN). To meet 1- $\mathrm {W}/{\mathrm {mm}}^{2}$ power-density target for high-performance computing (HPC) systems, a 25-high- $Q$ -factor (300 MHz), 150- $\mu \text{m}$ -thick, in-molding power inductor is provided for high-efficiency point-of-load (PoL) voltage regulation. Meanwhile, a novel analytical model for backside power delivery is developed for computer-aided-design (CAD) procedure to optimize the system efficiency. For the power flowing from bumps (57- $\mu \text{m} V_{\mathrm {DD}}$ -bump pitch) and backside PDN to active devices, the area resistances contributed by backside PDN and the buried power rail (BPR) are 23% and 77%, respectively, if a 10- $\mu \text{m}$ -horizontal-pitch nano- through-silicon via ( $n$ TSV) is available. The resulting impact on power dissipation is within 1% so negligible. A higher ratio (0.5) buck converter with maintained efficiency is combined to better benefit the external interconnect. The overall power delivery efficiency $\eta \,\,=83$ % can be obtained for 1- $\mathrm {W}/{\mathrm {mm}}^{2}$ power-density target. The power losses contributed by an air-core inductor, power switches, and PDN/BPR/redistribution layer (RDL) are 26%, 66%, and 8%, respectively.