Hello all. I'm trying to finish the layout of a inverter with sky130. There is a "li drawing" layer in the body of NMOS. Does anyone knows what kind of layer it represent? Thank you.

Local interconnect. It is the first metal layer. It is very resistive, so you should avoid using it for routing blocks, but it is ok for inner signals inside a logic gate like an inverter, for example.

Thank you so much!

Specifically, local interconnect is titanium nitride (TiN), which has a resistivity about halfway between aluminum and polysilicon.

That is very helpful. Thank you