Low-power silicon microheaters on a thin dielectric membrane with thick-film sensing layer for gas sensor applications

摘要

We report on the design, fabrication, and characterisation of a microheater module for chemoresistive, metal-oxide semiconductor gas sensors. The microheater consists of a dielectric stacked membrane with a polysilicon resistor heater element as well as a polysilicon temperature-sensing element. The geometry of both, the membrane and the heater have been optimised by means of finite element computer simulation in order to maximise heating efficiency. These devices complete of the sensing layer require only 30 mW to achieve a temperature of about 400 °C, while conventional thick film sensors fabricated on alumina substrates require typically more than 500 mW to reach the same working temperature. The proposed micromachining technology allows low-power microheaters to be fabricated at low cost and compatible with mass production technology; furthermore silicon micromachining is potentially suitable for the integration of the sensing and the heating element as well as the required electronics into the same battery-operated portable microsystem. The calibration curve of the sensor prototypes for various gases will be presented together with some future development about the microheater structure.