Characterization and patterning of novel high-TCR Ta–Si–N thin films for sensor application

Abstract

Temperature coefficient of resistance (TCR) and resistivity of films are crucial factors for thermal resistive sensors and concerned with microstructure. In this paper, a Ta–Si–N thin film with high negative TCR of −6250 ppm/°C at 30–100 °C has been fabricated on the silicon substrates by reactive co-sputtering at high nitrogen flow ratio (FN 2% = FN 2/(FN 2 + FAr) × 100%). It is larger than conventional materials, e.g. Pt, Cu, Ni and NiO x for thermal or flow sensors with TCR in the range of 2000–4540 ppm/°C. The microstructure and crystallinity of Ta–Si–N films were examined by X-ray diffraction. The resistivity and TCR were measured by the four-point probe and Keithley 2400 multimeter. The resistivity decreases with increasing temperature for the nature of negative TCR. The magnitude of both resistivity and TCR increases with increasing FN 2%. The patterning of high-TCR Ta–Si–N film on a flexible material has been performed by IC compatible processes, therefore it will be suitable for the integration with circuit design for the flexible sensor arrays in future.