Snap-3D: A Constrained Placement-Driven Physical Design Methodology for Face-to-Face-Bonded 3D ICs

3D integration technology is one of the leading options that can advance Moore's Law beyond conventional scaling. Due to the absence of commercial 3D placers and routers, existing 3D physical design flows rely heavily on 2D commercial tools to handle 3D IC physical synthesis. Specifically, these flows build 2D designs first and then convert them into 3D designs. However, several works demonstrate that design qualities degrade during this 2D-3D transformation. In this paper, we overcome this issue with our Snap-3D, a constraint-driven placement approach to build commercial-quality 3D ICs. Our key idea is based on the observation that if the standard cell height is contracted by one half and partitioned into multiple tiers, any commercial 2D placer can place them onto the row structure and naturally achieve high-quality 3D placement. This methodology is shown to optimize power, performance, and area (PPA) metrics across different tiers simultaneously and minimize the aforementioned design quality loss. Experimental results on 7 industrial designs demonstrate that Snap-3D achieves up to 5.4% wirelength, 10.1% power, and 92.3% total negative slack improvements compared with state-of-the-art 3D design flows.