Does anybody know, what are rules for creating a fill_config file for klayout ? I mean something like this:

<https://github.com/KrzysztofHerman/OpenROAD-flow-scripts/blob/ihp-platform/flow/platforms/sky130hd/fill.json>

one but for other technology (IHP130)

This json file is for OpenROAD not for KLayout. The rules for fill are dictated by the PDK. You can find the syntax here: https://github.com/The-OpenROAD-Project/OpenROAD/blob/master/src/fin/README.md#example-scripts

@Austin Rovinski thanks. I have already started to port this file into IHP PDK. I found also a USE_FILL variable, which is multiple times verified during the flow but seems to never be set.

USE_FILL

I believe has to be set in the design config file. It is not enabled by default.

ok, thanks!