BS-PDN-Last: Towards Optimal Power Delivery Network Design With Multifunctional Backside Metal Layers

The increasing demand to maximize PPA gains with backside metal layers has driven their function beyond power delivery. This study introduces a novel BS-PDN-last flow, crucial for leveraging multifunctional backside, by deferring power routing to the post-signal routing stage. This approach addresses the IR-drop and performance trade-offs inherent in conventional PDN-first flows. Experimental results show that the BS-PDN-last flow achieves a $90 \%$ reduction in Total Negative Slack and a $\mathbf{1 2 \%}$ performance gain with BS-CDN. Additionally, our work presents the first comprehensive comparison of FS-PDN, BSPDN, and multifunctional backside designs, evaluated on both physical design and workload metrics leveraging accurate vector-based analysis.