Toward Controllable Hierarchical Clock Tree Synthesis with Skew-Latency-Load Tree

Clock tree synthesis (CTS) constructs an efficient clock tree, meeting design constraints and minimizing resource usage. It serves as a bridge between placement and routing, facilitating concurrent optimization of multiple design objectives. To construct a clock tree with lower latency and load capacitance while maintaining a specified skew constraint, we introduce skew-latency-load tree (SLLT) which combines the merits of bound skew tree and Steiner shallow-light tree, along with an analysis and demonstration of the boundaries of these two tree types. We propose a method for constructing SLLT, which significantly reduces both the maximum latency and load capacitance compared to previous methods while ensuring skew control. Combining this routing topology generation method, we introduce a hierarchical CTS framework, and it is constructed by integrating partition schemes and buffering optimization techniques. We validate our solution at 28nm process technology, demonstrating superior performance compared to the solutions of OpenROAD and advanced commercial tool. Our approach outperforms in all metrics (max latency, skew, buffer number, clock capacitance), achieving a significant reduction in latency of 29.45% compared to OpenROAD and 6.75% compared to the commercial tool.