Microstructural and electrical characteristics of reactively sputtered ZrN x thin films

Abstract

The effects of nitrogen flow rate on the microstructure, composition and electrical properties of ZrN x films prepared by reactive sputtering were investigated by X-ray diffraction, field-emission electron probe micro-analyzer, transmission electron microscopy, X-ray photoelectron spectroscopy and four-point probe method. Results indicated that the ZrN x films were crystallized in NaCl-type structure and showed a near-stoichiometric composition at nitrogen flow rate of 3 SCCM. The existence of residual oxygen in the ZrN x films was ascribed to the relatively high base pressure attained in the present work. The residual oxygen atoms in the ZrN x films may possibly substitute the nitrogen atoms or occupy the interstitial positions in the ZrN lattice, causing that the so-called near-stoichiometric films and the delay of occurrence for over-stoichiometric films in the N/Zr ratio evolution with nitrogen flow rate. The slightly larger lattice constant of ZrN x films compared with the ideal value of ZrN compound demonstrated the presence of residual oxygen atoms in the films. The electron scattering effects due to impurity atoms may be enhanced by the incorporation of residual oxygen atoms and were responsible for the overall raise in the resistivity of ZrN x films as a function of nitrogen flow rate, comparing with the value reported by previous studies.