Since Finland and France are both Schengen members you will go through passport control at HEL, the first point of entry to Schengen.

As mentioned above, non-Schengen arrival gates are separate from others at HEL T2, and it's a bit of a walk to the immigration checkpoint. I haven't connected at HEL for a few years, just use it as an O&D airport, but if your flight from ORD arrives on time you should have enough time for passport control and a quick walk to the gate for the flight to CDG.

My most recent flights to HEL have been BA Tier Point runs, with one or two nights in the city. Immigration officers have raised an eyebrow when I say why I'm making such a quick trip but I've not been given aggro for short stays in Finland.