Fabrication of a novel micro liquid flow sensor using a TaN thin film

A micro flow sensor with high temperature coefficient of resistance (TCR) is very important because of its high sensitivity of flow sensors. Different from the conventional positive-TCR Pt film used in micro flow sensor with self-heating, higher negative-TCR micro flow sensor without self-heating is developed and fabricated in this research. The novel TaN-material micro liquid flow sensors are fabricated by reactive magnetron co-sputtering system at different nitrogen flow ratios. The magnitude of negative-TCR TaN films increases with increasing nitrogen flow ratios, so the high-TCR micro flow sensor can be prepared successfully at higher N₂ flow ratio. In order to understand the sensing ability, micro flow sensor is fabricated by MEMS technology. Measurement results show that this TaN micro flow sensor has high sensitivity of 407 ohm/(ml/min) at Re < 5, corresponding to volume flow rate of 0.167 ml/min. This device with high-negative-TCR materials can be beneficial for the measurement of low-velocity flow of liquid because of its high sensitivity at low Reynolds number.