Is moving to a higher layer for clock always helpful in reducing delay?

o   Moving to a higher layer is not always helpful in reducing delay. It's a trade-off.

o   Resistance (R): Higher layers have thicker wires, which decreases resistance. This part helps reduce delay (R×C).

o   Capacitance (C): While the area capacitance to the layers below might decrease due to greater distance, the fringe and coupling capacitance can increase because the wires are taller and have more surface area on their sides.

o    Conclusion: For very long nets, the benefit of lower resistance dominates, and using higher layers is helpful. For shorter nets, the increased capacitance can negate the benefit of lower resistance, potentially even increasing the total delay.