Hi all, Are vias (contacts) very expensive to be part of the layout routing? I know some rules like “we use Li only for very little distances (local) routing and M1/M2 are the best options for global routing and M3 is usually used for IP’s PWR/GND delivery.” But in general, are there some rules/practical ways to prioritize layers for routing in a custom/analog layout design (I mean non-experimental/non-experience-based ways, which rookies like me could use them)?

rules are simple: 1. Use one direction of routing for each layer (to avoid cases where you cant route anything without having to reroute other nets) 2. Maximize width 3. Avoid vias, but if you need to, place as many as you can. 4. Use as higher level metals as possible because they have lower resistance. If capacitance is an issue then use below layers, but avoid LI1

1. #3 and #4 are kind of contradictions. 2. I saw many custom designs which use a layer with both H and V directions. 3. Using one layer for V and the other for H will make you switch b/w them and cost a lot of vias. 4. Imagine we use M2 as the base metal for routing. if we have to go to M1 because of some congestions then should we come back to M2 again? IMHO it is not that simple because of a lot of trade-offs. 😄