Fabrication and characterization of a double-heater based MEMS thermal flow sensor

This paper presents a micro flow sensor based on two heaters acting also as temperature sensors. The two heating/sensing elements of the sensor are arranged in the diagonal arms of the Wheatstone bridge and suspended in an airflow channel by solid beams. The length of the heater and the distance between the heaters were optimized by numerical modeling. The solid beams were fabricated by a heavily doped p-type silicon layer and a silicon nitride layer, which was immune to airflow disturbances and thermal noises. The experimental results indicated that the micro flow sensor with a high sensitivity of 0.30 mV/(ml/min) exhibited an excellent linear response within the range of 0.5–6 sccm. This micro sensor demonstrated great potentials in biological applications, micro gas chromatography systems, medical instrumentation and process control.

► The device with two heaters working as temperature sensing elements is proposed for the first time.
► The fabrication process of the MEMS based gas flow sensor with optimum heater length and the heaters distance was presented.
► The micro gas flow sensor was applied to flow rate measurement with characterization results described and discussed.