Surface and interface structural analysis of W deposited on 6H–SiC substrates annealed in argon

Abstract

A study of a tungsten (W) thin film deposited on a single crystalline 6H–SiC substrate and annealed in Ar at temperatures of 700 °C, 800 °C, 900 °C and 1000 °C for 1 hour was conducted. The subsequent solid state reactions, phase composition and surface morphology were investigated by Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM) analysis techniques. RBS analysis of as-deposited samples indicated the presence of W and oxygen in the as-deposited thin film, the GIXRD analysis of the as-deposited film showed the presence of W, WO₃, W₅Si₃ and WC. RBS results of the sample annealed at 700 °C indicated interaction between W and SiC with the formation of a reaction zone. The GIXRD analysis indicated the presence of W₅Si₃, WO₃, SiO₂, W₂C and WC in the W–SiC reaction zone (RZ) after annealing at 700 °C. At temperatures of 800 °C to 1000 °C, the W–SiC samples did not show any new phase formation from the GIXRD patterns, while the RBS results indicate an increase in the RZ width which meant further reactions were taking place. An increase in the peak intensities of the GIXRD patterns was observed due to a change in the polycrystalline nature of the W film to a more crystalline structure. SEM micrographs of the as-deposited samples indicated that the W thin film had a uniform surface with small grains. Annealing at 700 °C and above led to the formation of large crystals. The large crystals formed were randomly orientated; it was observed that an increase in annealing temperature led to an increase in the film crystal size forming pores between crystals.