I want to go to USA or Canada for exchange, but where can I study nanotechnology?
There are lots of places in Canada:
The University of Alberta has micro / nanofabrication facilities, and surrounds the National Institute for NanoTechnology (technically, government research, but in practice, most of its Ph.D. researchers are cross-appointed to the University, and the graduate students affiliated there). I say next door, but it's actually on campus, and people go back and forth for the various facilities.
But really, it depends on what you want to study, and what your background is. Nanotechnology is a big field (if you'll pardon the pun).
Separate names with a comma.