Effect of reactive gases flow ratios on the microstructure and electrical resistivity of Ta–N–O thin films by reactive co-sputtering

Abstract

A combination of the beneficial properties of tantalum oxide and tantalum nitride may result in a new and functional tantalum oxynitride (Ta–O–N). In this paper, Ta–O–N thin films were fabricated by using reactive magnetron sputtering at different reactive gas ratios. The ratio of reactive gases to total flow gases was controlled from 6% to 30%. The microstructure, composition, chemical bonding, morphology and resistivity of the Ta–O–N thin films were characterized. Increasing reactive gas flow ratio will result in the increase of the O/(O + N) ratio in Ta–O–N from 0.22 to 0.79. All films were quasi-amorphous structures in this study. The higher reactive gas flow ratio led to more disorder or amorphous microstructure with a broader diffraction peak. The position of the highest intensity peak about 36° shifts downward with increasing O/(O + N) ratio because of the sufficient Ta–O phase formation. The FTIR absorption bands at 500–800 cm − 1 corresponding to Ta–O–Ta and Ta–O stretching vibration modes were observed . A weak absorption band at 800–1000 cm − 1 was the tantalum suboxides. The resistivity increased from 288 μΩcm (conducting) to 11,540 Ωcm (semiconducting–insulating) with increasing O/(O + N) ratio. The oxygen content dominates the microstructure formation and resistivity of the Ta–O–N system compared to nitrogen.