Study of Ni–Cr / CrN bilayer thin films resistor prepared by magnetron sputtering

Abstract

In this study, we prepare bilayer Ni–Cr/CrN films. A Ni–Cr resistive thin film was prepared by DC sputtering from targets of Ni0.8-Cr0.2 casting alloy. A CrN protection thin film was prepared based on optimum sputtering conditions of the Ni–Cr film, which was made by DC and RF magnetron co-sputtering from targets of Ni0.8-Cr0.2 casting alloy and chromium. The electrical properties and microstructures of the resistive films at different annealing temperatures were investigated. The phase evolution, microstructural and composition of Ni–Cr and NiCr/CrN films were characterized by X-ray diffraction (XRD), field-emission transmission electron microscopy (HRTEM) and auger electron spectroscopy (AES). The results indicated that the resistivity of the bilayer Ni–Cr/CrN films is higher than Ni–Cr films. When the annealing temperature was set to 300 °C, the bilayer Ni–Cr/CrN films exhibited a resistivity ∼303 μΩ cm with the smallest temperature coefficient of resistance (TCR) of −3 ppm/°C. However, the Ni–Cr films that annealed at 300 °C showed a resistivity of ∼210 μΩ cm, with a TCR of 13 ppm/°C. In addition, the TCR and resistivity variation rate of CrN protective coating layer on the Ni–Cr films after high temperature testing at 150 °C up to 100 h was done. The results show that the average change rate of the TCR for bilayer Ni–Cr/CrN films is lower than single Ni–Cr films.