Multi-layer global routing considering via and wire capacities

Abstract

Abstract-Global routing for modern large-scale circuit designs has attracted much attention in the recent literature. Most of the state-of-the-art academic global routers just work on a simplified routing congestion model that ignores the essential via capacity for routing through multiple metal layers. Such a simplified model would easily cause fatal routability problems in subsequent detailed routing. To remedy this deficiency, we present in this paper a more effective congestion metric that considers both the in-tile nets and the residual via capacity for global routing. With this congestion metric, we develop a new global router that features two novel routing algorithms for congestion optimization, namely least-flexibility-first routing and multi-source multi-sink escaping-point routing. The least-flexibility-first routing processes the nets with the least flexibility first, facilitating a quick prediction of congestion hot spots for the subsequent nets. Enjoying lower time complexity than traditional maze and A*-search routing, in particular, the linear-time escaping-point routing guarantees to find the optimal solution and achieves the theoretical lower-bound time complexity. Experimental results show that our global router can achieve very high-quality routing solutions with more reasonable via usage, which can benefit and correctly guide subsequent detailed routing.

A local congestion elimination technique driven by overflow

“…There have been several pioneering works laying emphasis on the congestion estimation, since the early prediction in the physical design flow is critical to reduce design turnaround time and cost [5], and can avoid generating an unroutable design. Several recent works devote to studying prediction model by concentrating on the factors that affect congestion [6,7,8,9]. Others use probabilistic congestion estimation techniques [10,11].…”