How do I prevent mini cheesecakes from stick in muffin pan
My first choice would be to get a bunch of small spring molds for round cakes. That probably would be my first choice if you really didn't want to use cup cake liners. 

If you really want squares, then I think your best bet is to use parchment paper. Cut the parchment paper to fit the full cup, then carefully fold it at the corners just so, so that the uncooked cheese cake will fill the cup without wrinkles. It will take some trial and error, but once you figure out the correct angles, it should be easily to duplicate. You would then need to carefully remove the cakes from the parchment cups you made, but that should be much easier than trying to get them out of the pan if they've stuck.

Alternatively, you could try silicone moulds, but I don't know whether the cheese cake would be too sticky or too soft for that or not.