AlN films, grown by nitrogen or argon ion beam-assisted pulsed laser deposition, exhibit very high stresses at a certain ion energy These stresses are mainly caused by ion beam-induced defects. The magnitude of stress is found to depend not only on the ion energy, but also on the deposition temperature and the ion incidence angle. To explain the relation of the observed film stresses and the appropriate deposition parameters, a simple model was developed. The model takes into account the annealing of a certain fraction of the ion beam-induced point defects by thermal diffusion towards the film surface, which acts like a sink of the defect concentration. This model allows us to predict the ion energy where the point defect concentration in a film reaches a maximum in agreement with the experimental observation of the stress maximum.