THE SI PLANAR PELLISTOR - A LOW-POWER PELLISTOR SENSOR IN SI THIN-FILM TECHNOLOGY

A novel pellistor sensor structure has been fabricated by Si micromachining technology and tested for the measurement of combustible gases. The Si planar pellistor is a small gas sensor (850-mu-m2) using the heat of reaction in an oxygen atmosphere or the heat of thermal decomposition in a non-oxygen atmosphere as a measure of the gas concentration. In the simplest form a metallic meander resistor serves as the heater, the temperature sensor and the catalyser of the sensor element. The thermal insulation and the mechanical suspension between the heated sensor and the substrate are realized by a thin (150 nm) LPCVD Si3N4 membrane. The preparation and results of measurements are presented and the optimization of the structure with respect to the sensor dimensions and the variation of temperature over the sensing area is discussed.