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

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 (FN2% = FN2/(FN2 + FAr) × 100%). It is larger than conventional materials, e.g. Pt, Cu, Ni and NiOx 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 FN2%. 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.