An ultrasensitive silicon pressure-based microflow sensor

An ultrasensitive silicon pressure-based flowmeter has been developed for use in measuring sub-SCCM gas flow in semiconductor process equipment. The device utilizes a capacitive pressure sensor to measure the pressure drop induced by flow across a micromachined silicon flow channel. The flowmeter is fabricated using a single-sided dissolved-wafer process and requires only six masks. The capacitive pressure sensor uses a thin (2.9 mu m) stress-compensated membrane, which enables the sensor to monitor differential pressures as low as 1 mtorr while withstanding overpressures greater than 700 torr. Creep and fatigue change the offset by>