Most likely to be sticking contacts in relay/timer . Unlikely to be switch as power to switch is shut off when ignition not on .
Locate the wiper relay/timer near to fusebox inside car. There will probably be a few relays next to each other. Wiper relay is often but not always a different colour/size to other relays as it also has timer inside. If wipers are still running feel if one of them is warm to touch. Give it a sharp tap with a screwdriver handle or similar blunt instrument. This may open the contacts and stop the wipers.
Failing that remove each relay one at a time .....when wipers stop you know you've found the correct one. Be aware you may need a strong finger grip as they can be stubborn pigs to remove. Do not attempt to lever a relay out of it's socket with a screwdriver blade as the metal blade may touch 2 terminals and cause a short circuit (not recommended). best of luck !
PS....I'm assuming you know what a relay looks like....it's a little plastic box with terminals on one side where it plugs into the socket.....about 1inch x 1inch x 1inch in size .
mic the spanner, November 2008
