Let’s assume I have two clock metal routing nets, and I don’t have space in the layout for shielding those two nets. What should I do?

If you don't have space for shielding the two clock metal routings, you can take the following steps:

Increase Spacing: If shielding is not possible, try to increase the spacing between the two clock nets as much as possible. This reduces capacitive coupling and helps mitigate crosstalk.

Use Higher Metal Layers: Move one of the clock routes to a higher metal layer. Higher layers typically have lower resistance and capacitance, which can reduce the impact of coupling between the two nets.

Reduce Routing Path of Metal: Reroute the clock paths to avoid long parallel runs, minimizing the length over which the two clocks are coupled, thus reducing the risk of interference.

These strategies help to maintain signal integrity even without dedicated shielding.