What if timing is critical and spreading isn't an option?

Delay is due to cell and interconnect. When area is congested, when tool calculates timing, it may consider detour routes, adding more delay.

When cells are spreaded just enough to solve congestion, it may reduce route length as well, helping in congestion and timing both.

Instead of broad spreading, use more localized techniques: Apply partial blockages with lower blockage percentages (e.g., 10%) only in the absolute peak congestion GCells, rather than large areas.

Guide Routing: routing constraints can be applied later (during routing stage) to force certain nets onto less congested higher metal layers

Timing-Aware Congestion Reduction: Use placement modes or options that explicitly try to balance timing and congestion (place_opt -congestion -timing_driven in some tools). The tool will try to spread cells just enough to ease congestion while minimizing the impact on critical path delays.