Characterisation of Process Variables for Ultraviolet Assisted Injection Liquid Source Chemical Vapour Deposition (Uvils-Cvd) of Tantalum Pentoxide Films

Abstract

ABSTRACTThe characterisation of the physical and chemical properties of tantalum pentoxide (Ta2O5) films, deposited on silicon using a newly developed low temperature deposition technique - ultraviolet assisted injection liquid source chemical vapour deposition (UVILSCVD), is reported. The effect of deposition parameters including substrate temperature, oxidising agent (N2O) flow, precursor carrier gas (Ar) flow, number of drops of precursor injected and precursor solution concentration is discussed. Spectroscopic ellipsometry (SE) was used to determine the refractive index and thickness of the Ta2O5films. The film thickness was observed to increase with temperature, number of injected drops and precursor solution percentage, while the refractive index was found to be most sensitive to temperature. SIMS measurements showed good agreement with extracted thickness values. Fourier transform infrared spectroscopy was used to identify and monitor Ta2O5(pentoxide), TaO2and TaO (suboxide) formation via curve fitting analysis of spectral features. Results showed increased suboxide formation as a function of increasing pressure and as a function of decreasing N2O flow, precursor solution concentration and number of drops injected. The summation of the areas under peaks characteristic of the tantalum-oxygen bonding correlated well with the thicknesses determined by spectroscopic ellipsometry. The FTIR spectra revealed a dramatic increase in the proportion of suboxide in the absence of the oxidising gas.