Abstract: The time-dependent temperature distribution of thin aluminium films with a layer of dielectric passivation, emphatically the influence of the kind and the thickness of dielectric films on this distribution, has been studied numerically using the finite difference method. It shows that the peak temperature and temperature gradient of thin aluminium films can be greatly reduced by using dielectric passivation of Si₃N₄(or Al₂N₃) with high thermal conductivity which is very beneficial to improving electromigration lifetime and anti-surge-current ability of aluminium films.