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As state-of-the-art 3-D IC place-and-route flows were designed with older technology nodes and aggressive bonding pitch assumptions, they introduce an unacceptable number of 3-D via overlap violations during routing in real-world scenarios. Specifically, when dealing with higher via pitch to wire size ratios using more advanced technology nodes than they were designed for, these flows struggle to comply with width and spacing rules. In this article, we propose a novel 3-D via legalization stage and a subsequent refinement stage during routing to address this issue. Two independent via legalization methods are introduced: a force-based algorithm and a bipartite-matching algorithm with Bayesian optimization. Our two legalization methods, along with the refinement stage, are compatible with various process nodes, bonding technologies, and partitioning styles. By implementing the modified 3-D routing with the proposed legalizers, we successfully eliminate all 3-D via overlap violations while minimizing the impact on performance, power, or area.

3-D integration technology is one of the leading options to advance Moore’s Law beyond conventional scaling. One of the 3-D integration choice is the heterogeneous integration with the benefits of power saving over the homogeneous integration. With the lack of commercial 3-D tools, existing 3-D physical design flows utilize 2-D commercial tools to perform 3-D integrated circuit (3-D IC) physical synthesis. Specifically, these flows build 2-D designs first and then convert them into 3-D designs. However, several works demonstrate that design qualities degrade during this 2-D–3-D transformation and some of the flows do not support heterogeneous integration. In this article, we propose Snap-3D, a constraint-driven placement approach to build commercial-quality 3-D ICs, which supports both homogeneous and heterogeneous 3-D ICs. Our key idea is based on the observation that if the standard cell height is contracted and partitioned into multiple tiers, any commercial 2-D placer can place them onto the row structure and naturally achieve high-quality 3-D 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 seven industrial designs demonstrate that Snap-3D achieves up to 10.9% wirelength, 9% power, and 25% performance improvements compared with state-of-the-art 3-D design flows.