Influence of process conditions on chemical composition and electronic properties of AlN thin films prepared by ArF reactive pulsed laser deposition

Aluminium nitride (AlN) thin films were deposited using a reactive ArF excimer pulsed laser ablation (PLD) of a pure Al target in a N-2 plasma atmosphere, generated by a RF source, onto p-Si < 100 > substrates, at increasing substrate temperatures. A radio-frequency (13.56 MHz RF) apparatus was introduced with the specific aim of increasing the fraction of excited and/or ionized nitrogen species and, ultimately, to increase its reactivity toward the aluminum atoms, expanding in the plume, and the formation of AlN. We studied the dependence and correlation of structural, compositional and electric properties with the specific experimental conditions. The chemical composition of films, determined by XPS spectroscopy, revealed a trend of increased N-2 reactivity, uptake and nitride formation, with deposition temperature. Electrical resistivity, measured by the four-point-probe method, has been found to be also strongly dependent on the substrate temperature and nitrogen incorporation. A possible explanation of the correlation of surface conductivity with chemical composition is suggested and discussed.