@User Have a look at https://codeberg.org/tok/librecell/src/branch/master/librecell-lib. You'll find a tool called lctime that uses ngspice to for characterization. I believe @User has some experience with it.

thanks

That work with pdk skywater 130?

Yes, we have been using it with Sky130

How? In the instructions of the repository only say with 45nm

You have to use the Spice models of Sky130