Conceptual Design of a Resonant Pirani Gauge Toward Wide-Range Pressure Sensing

This letter reports a CMOS-microelectromechanical system (MEMS) pressure sensor comprising a double-ended tuning fork capacitive resonant transducer and a Pirani gauge thermal transducer in a single device configuration, which demonstrates a wide-range pressure sensing capability, small form factor, and sensor fusion. The device integrated with an interfaced circuit was fabricated through a 0.35-
μ
m CMOS foundry process, together with an in-house release process. Thanks to the resonant transducer which is sensitive to pressure due to squeezed-film damping effect, the high pressure sensing range is achieved by measuring resonant frequency shift, whereas the medium pressure region is sensed by quality factor (
Q
) change of the resonator. As a result, a full-scale range of 10–760 torr is realized by the proposed CMOS-MEMS pressure sensor using its resonant transducer. To further extend the measurement range to the lower pressure range, an embedded thermal transducer of the device is used to serve as Pirani gauge that is capable of detecting pressure from 0.02 to 10 torr by the use of thermal resistance
$(R_{{\rm{th}}})$
change. Through a simple algorithm combining variations of
Q
, resonant frequency
$f_{o}$
, and thermal resistance
$R_{{\rm{th}}}$
, the proposed resonant Pirani gauge pressure sensor features a very wide-range pressure sensing capability from 0.02 to 760 torr.