1st off, you need some process to give an undercut sidewall
so that the excess Al (to be lifted off) is not connected to
the Al that remains on your wafer.

2nd, you won't be able to lift off 1 um thick Al with only 1
um thick resist.  You will need at least 2 um thick resist
(at least 2x the thickness of the metal).

Hope this helps.
Bill