The dependence of aluminum nitride film crystallography on sputtering plasma composition

Aluminum–nitrogen films were grown on unheated substrates by rf diode sputtering an aluminum target in Ar/N2 atm. Optical emission spectroscopy was used to monitor excited nitrogen species in the sputtering plasma. X-ray diffraction results, supported by Auger electron spectroscopy for chemical analysis, show that films deposited on Si- and SiO2-coated Si evolve from polycrystalline fcc Al to semiamorphous AlN to basal orientation hcp AlN as the sputtering gas N2 content is increased. The transition from metal to nitride film growth is correlated with a steplike decrease in the growth rate which is characteristic of compound formation at the target, and occurs subsequent to a rapid increase in excited N+2 species in the plasma. This correlation is discussed in terms of processes involving N+2 which produce active N species in the discharge.