Integrated micromachined gas multisensor for domestic boilers

This work describes the design and characterization of a micromachined integrated gas multisensor for detection and control of the pollutant emissions in a domestic boiler. Mechanical, thermal and sensing properties have been investigated via simulation and experiments. The proposed design takes advantages of the small thermal inertia involved in the mass of the micromachined structure which has low power consumption to reach the working until 585°C, and quick response times, lower than 20 ms. The gas sensor fabrication is based on a standard CMOS technology. The manufactured sensors consist of a thin dielectric membrane as carrier structure for a SiO₂ passivated polysilicon heater that is the support of the sensing material. The microsystem contains four independent membranes. So, the proposed procedure allows depositing different sensing materials in each one of the membranes of the multisensor in order to have an integrated sensor for different gases such as CO, NO_x and O₂. Prototypes have been manufactured and examined considering sensitivity, power consumption and thermal response time in relation to different timing and/or periodic operation modes used as heater signal.