Thin tantalum and tantalum oxide films grown by pulsed laser deposition

Abstract

The growth of tantalum and tantalum oxide films grown on Si (100) and quartz by 532nm (Nd:YAG) pulsed laser deposition (PLD) in various O2 gas environments has been investigated. Ellipsometry has been used to determine the refractive index and thickness of the films whilst Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and UV spectrophotometry were used to identify tantalum and tantalum oxide formation and optical transmittance as well as optical constants. The FTIR, XPS and UV spectra reveal a strong dependence of the film properties on the O2 gas pressure used. The results showed that oxygen pressure could be used to control the composition of the films. XPS analysis showed that the composition of the layers changed from Ta2O5 to metal tantalum as the oxygen pressure was varied from 0.2 to 0.005mbar. Under optimum deposition conditions, the refractive index of the oxide layers was found to be around 2.10±0.05 which is close to the value of the bulk Ta2O5 of 2.2 while an optical transmittance in the visible region of the spectrum up to 90% was obtained. These properties compare very favourably with those of films produced by other techniques.