Monolithic CMOS multi-transducer gas sensor microsystem for organic and inorganic analytes

A monolithically integrated multi-transducer microsystem to detect organic and inorganic gases is presented. The system comprises two polymer-based sensor arrays based on capacitive and gravimetric transducers, a metal-oxide-based sensor array, the respective driving and signal processing electronics and a digital communication interface (see the first figure). The chip has been fabricated in industrial 0.8-μm, complementary-metal-oxide-semiconductor (CMOS) technology with subsequent post-CMOS micromachining. The simultaneous detection of organic and inorganic target analytes with the single chip multi-transducer system has been demonstrated. The system is very flexible and can provide different information of interest: the capacitive sensors can, e.g., act as humidity sensors to deal with the cross-sensitivity of the metal-oxide-based sensors to water, or the capacitive sensors can be coated with differently thick polymer layers to detect organic volatiles even in a background of water. The multi-transducer approach provides a wealth of information that can be used to improve the system discrimination capability and performance in gas detection.