Influence factors of aluminum nitride deposition investigated by molecular simulations

Abstract

The effects of substrate surface polarity, substrate temperature and deposition rate on the AlN growth with chemical vapor deposition method were studied with the Stillinger–Weber potential. The differences in crystal structures, growth modes, and surface topography at the molecular level were discussed. For N-polar surface, the growth mode of AlN film is mainly vertical-direction growth mode. During the physical adsorption process, the N atoms have a high surface diffusion coefficient (≥ 2 × 10^–11 m²/s), due to the low attraction between N-polar AlN substrate surface and the deposited lightweight atoms (N atoms), causing the N atoms to collide with others and form large clusters, thereby leading to a vertical-direction growth mode. For Al-polar surface, the atoms have a low surface diffusion coefficient (≤ 2 × 10^–12 m²/s), causing the atoms to bond with the surface atoms quickly and leading to horizontal-direction mode and bilayer growth while maintaining consistent surface polarity. High temperatures promote the cleavage of Al–Al and N–N bonds and facilitating Al–N bond formation through atomic vibrations and translations. High deposition rates lead to increased cluster formation, limiting the time and space for rearrangement of chemically adsorbed atoms. High temperature and low deposition rate are conducive to the smoother surface morphology of the resulting AlN film and lead to the more ordered hexagonal structure. From the results, during the deposition process, high temperature, the Al-polar surface, and low deposition rate are favorable for epitaxial growth of AlN. Finally, the AlN grown on the Al-polar AlN surface contains a small area of N-polar region was studied and the repairmen mechanism of N-polar region is observed.