Photo-deposition of tantalum pentoxide ®lm using 222 nm excimer lamps

In this paper, we report the growth of thin tantalum pentoxide ®lms 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 ®lms formed have been studied using ellipsometry, UV spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). It was found that the ®lms can be deposited at substrate temperatures as low as 258C. The kinetic study of the reaction processing indicated that at low deposition temperatures between 25 and 1008C, the deposition process is a condensationcontrolled mechanism whilst at high deposition temperatures between 100 and 4008C 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 in¯uence of the deposition temperature on the ®lm properties and its optimisation are discussed. At temperatures above 1008C the ®lm thickness increased with temperature while it decreased as the temperature is below 1008C. The refractive index and the optical band-gap of the ®lms 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. # 2000 Elsevier Science B.V. All rights reserved.