Characteristics of tantalum nitride thin film strain gauges for harsh environments

This paper presents the characteristics of Ta-N thin film strain gauges that are suitable for harsh environments, which were deposited on thermally oxidized Si substrates by dc reactive magnetron sputtering in an argon-nitrogen atmosphere (Ar-N2 (4-16%)). These films were annealed for 1 h in 2 × 10−6 Torr in a vacuum furnace with temperatures that ranged from 500 to 1000 °C. The optimized deposition and annealing conditions of the Ta-N thin film strain gauges were determined using 8% N2 gas flow ratio and annealing at 900 °C for 1 h. Under optimum formation conditions, the Ta-N thin film strain gauges obtained a high electrical resistivity, ρ = 768.93 μΩ cm, a low temperature coefficient of resistance, TCR = −84 ppm/°C and a high temporal stability with a good longitudinal gauge factor, GF = 4.12. The fabricated Ta-N thin film strain gauges are expected to be used in micromachined pressure sensors and load cells that are operable under harsh environments.