Below is excerpted from a well-known professor's site:
Some signals cause a process to stop: SIGSTOP (stop!), SIGTSTP (stop from tty: probably ^Z was typed), SIGTTIN (tty input asked by background process), SIGTTOU (tty output sent by background process, and this was disallowed by stty tostop).
Apart from ^Z there also is ^Y. The former stops the process when it is typed, the latter stops it when it is read.
I know what Ctrl+Z means under Linux, however, I don't know what Ctrl+Y does.