Characteristics of tantalum nitride thin film strain gauges for harsh environments

Abstract

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 1h in 2×10−6Torr 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 1h. Under optimum formation conditions, the Ta–N thin film strain gauges obtained a high electrical resistivity, ρ=768.93μΩcm, a low temperature coefficient of resistance, TCR=−84ppm/°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.