GROWTH-MECHANISM OF CUBIC BORON-NITRIDE THIN-FILMS BY ION-BEAM ASSISTSPUTTER-DEPOSITION

Cubic boron nitride (c-BN) thin films were successfully grown on Si(10 0) substrates by dual ion beam sputter deposition and the growth mecha nism was studied with angle resolved in situ x-ray photoelectron spect roscopy (XPS) analysis. Boron was sputter deposited by 1 keV argon ion s from a boron target and simultaneously bombarded with low energy nit rogen and argon ions mixture. Through Fourier transform infrared absor ption spectroscopy (FTIR) and in situ XPS experiment, the optimum cond itions for the c-BN growth such as the substrate temperature, the assi st ion current density and the ion energy were determined to be 460 de grees C, 60 mu A/cm(2) and 350 eV, respectively. Angle resolved in sit u XPS analysis showed that the 1.2+/-0.2 nm surface layer of the c-BN film is always in the hexagonal boron nitride (h-BN) phase, which clea rly shows that c-BN phase grows by the transformation from the initial ly formed h-BN phase by low energy ion bombardment. Cross-sectional hi gh resolution transmission electron microscopy (TEM) images show that the BN thin films on Si has a sequential layered structure which consi sts of an initial amorphous BN (a-BN) layer (similar to 4 nm), a trans itional h-BN layer (similar to 5 nm), and a main c-BN layer. The trans formation of the h-BN to the c-BN phase and the unusual sequential lay ered structure were discussed in view of the compressive stress model. (C) 1997 American Vacuum Society.