Detection of low NO2 concentrations with low power micromachined tin oxidegas sensors

Semiconductor gas sensors integrated on silicon substrates with thermally i solated structures are presented and technological processing steps of thei r fabrication are described. Tin oxide sensitive layers have been deposited by reactive sputtering technique due to the compatibility with IC fabricat ion. The active area has a size of 500 x 500 mu m(2) and is supported by a membrane of silicon nitride. Polysilicon is used as heating material and th e power consumption is below 50 mW at the operating temperature of 350 degr ees C for every sensor prepared. Good isolation among chip devices was guar anteed from FEM thermal simulations [A. Gotz, I. Gracia, C. Cane, E. Lora-T amayo, M.C. Horrillo, J. Getino, C. Garcia, J. Gutierrez, A micromachined s olid state integrated gas sensor for the detection of aromatic hydrocarbons , Sensors and Actuators B 44 (1997) 483-487.]. Very low concentrations of N O2 have been detected with such type of device obtaining good sensitivity a nd short response time for various thin-film thicknesses of tin oxide. (C) 1999 Elsevier Science S.A. All rights reserved.