A SILICON THERMOCAPACITIVE FLOW SENSOR WITH FREQUENCY-MODULATED OUTPUT

A silicon thermocapacitive gas-flow sensor with frequency modulated ou tput where the shift in the oscillation frequency is related to the ga s-flow velocity has been developed. The sensing module, which is fabri cated using a MOS-compatible process combined with EDP groove etching, is a capacitor. The dielectric material of the capacitor is r.f.-sput tered SrTiO3, the large dielectric constant of which is also temperatu re dependent. Together with an external 555 IC, the oscillator frequen cy at zero flow velocity and 250 mW of heater power is 8.7 kHz. The se nsitivity is 118 Hz (m s(-1))(-1) in the linear region, with 250 mW of heater power.