Abstract
Monte Carlo simulations of via filling have been performed using the lattice model of crystal growth, which allows vacancy formation in the film during the growth. Adsorption, desorption and surface diffusion of adatoms are taken into account. Using a two-dimensional model, we examined the film growth from the initial surface with hollow parts (wedge-shaped and flat-bottomed holes), the aspect ratio of which ranged from 0.5 to 4. When a wedge-shaped hole is filled with deposited atoms, small voids appear in the film, which are aligned in the growth direction. In the case of the flat-bottomed hole, on the other hand, large voids with several hundred vacant sites appear in the middle of the hole. The voids are elongated in the growth direction as the aspect ratio becomes large. These voids have a similar structure to those of the experiment of filling vias and trenches in Cu interconnections from the solution without additives. The mechanism of the void formation is discussed in relation to the aspect ratio and the overpotential.
