Hi, can I make open pads (on metal 5) on efabless caravan? something like this project

Yes, you can. A number of chipIgnite users have made their own probe pads and even wirebond pads inside the user area. The only requirement is to make sure that Efabless knows that you need to get bare die back, so that you don't end up with packaged parts.

And metal5 is expose? Do you have an example of how the layout of the pad looks like? And last question, what is the minimum size of the pad and minimal distance from pad to pad?

Yes, metal 5 is exposed if you add the "pad" layer on top of metal 5 ("pad" is the sky130 term; in magic the layer is traditionally called "glass" for "glass cut"). See https://skywater-pdk.readthedocs.io/en/main/rules/periphery.html#pad. There is only a rule for pad-to-pad (meaning glass cut) distance. I do not know why they do not have a minimum width rule. Stick with the pad design from the I/O cells if you want to be safe (the pad itself, which is just metal 5 and glass cut with a metal 4 ring around the perimeter, has its own cell, which is called

sky130_fd_io__pad_esd

). Otherwise, the size of the cut depends on what you have for a wafer probe.

Thank you