Usually slotting rules are made to prevent delamination, so the "huge metal" rules would not really address that. Anyway, the Calibre stress rules seem to only check for slotting in what SkyWater defines as the "critical area" which is around the padframe. They don't seem to care what goes on in the middle of the chip.

SkyWater doesn't seem to require slotting. The main purpose of slotting in this process would be to minimize 'dishing,' which happens during the CMP - copper wires with different widths will experience different amounts of dishing. So, wires with different widths will not be well matched.

@Borivoje Nikolic: There were some variants of the original SkyWater s8 process that had copper wiring, and all of the maximum metal width rules apply only to those variants. But they have dropped all copper support for the sky130 (s130) process. It's all aluminum.

Correct. No need for slotting.

Maybe. I have worked with similar processes---also aluminum wiring---that had maximum width rules or required slotting. It's not uncommon.

I have seen the same - but typically as a waivable rule (it is there for matching).