Micro-pressure sensors made of indium tin oxide thin films

The microstructure, electrical resistivity and piezoresistive property of magnetron sputtered indium tin oxide (ITO) films were investigated as functions of preparation and post-annealing conditions. Annealing at 400 °C for 30 min resulted in low electrical resistivity ≤6.0 × 10−3 Ω cm and observable piezoresistive coefficient ranging from −4.3 × 10−11 to −7.1 × 10−11 Pa−1. Prototypes of pressure sensors with an annealed ITO film deposited on a 25 μm thick silicon diaphragm were fabricated. With a bias voltage of 1 V, the device gave a voltage response of 12.6 mV when the differential pressure across the diaphragm varied from −6 × 104 to 6 × 104 Pa.