At the front side of a wafer cassette fitted to a wafer feeding unit of a magnetic levitation wafer conveying device, a wafer stopper for preventing the wafer waiting in the wafer cassette from popping out is provided. The wafer supplied from the magnetic levitation conveying device is supplied into...http://www.google.ca/patents/US5747780?utm_source=gb-gplus-sharePatent US5747780 - Apparatus for conveying and processing a wafer in a physically contact-free state 
