Photo-deposition of tantalum pentoxide film using 222 nm excimer lamps

In this paper, we report the growth of thin tantalum pentoxide films on Si (1 0 0) and quartz by photo-induced chemical vapour deposition (photo-CVD) using a 222 nm excimer lamp. The properties of the films formed have been studied using ellipsometry, UV spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). It was found that the films can be deposited at substrate temperatures as low as 25°C. The kinetic study of the reaction processing indicated that at low deposition temperatures between 25 and 100°C, the deposition process is a condensation-controlled mechanism whilst at high deposition temperatures between 100 and 400°C a reaction-controlled mechanism is dominant during the growth with an activation energy of 0.08 eV, which is much lower than that of 2.2 eV for thermal-CVD processing. The influence of the deposition temperature on the film properties and its optimisation are discussed. At temperatures above 100°C the film thickness increased with temperature while it decreased as the temperature is below 100°C. The refractive index and the optical band-gap of the films were found to be around 2.09±0.05 and 4.10±0.05 eV, respectively, while an optical transmittance between 85 and 98% in the visible region of the spectrum was obtained at different thicknesses.