Fabrication and Characterization of Surface-Micromachined Compact Microheater for Gas Sensing Applications

A surface-micromachined compact microheater for gas sensing applications fabricated on a silicon substrate is presented. The heater was fabricated with a compatible CMOS process and its membrane was released using XeF₂ isotropic silicon etching. The membrane had SiO₂/Si_xN_y/SiO₂ layers (0.4/0.3/0.3 mum) in order to restrict the initial stress after the release, resulting in less than 2.5 mum height deviation from the membrane center to the anchor. The circular-type Pt (0.18 mum) heater proposed in this paper has a diameter of 110 mum and a width of 5 mum. It also shows a 4-probe measured heater resistance of 10.9 Omega, while that of the theoretical heater is 8.5 Omega. Also, to evaluate its thermal performance, the MEMS heater was characterized using an empirical parameter extraction method. As the total thermal loss coefficient of the heater (G,A) was modeled to 1.68e-5 W/K at ambient temperature (T_amb, 293 K) and the temperature coefficient of resistance at room temperature (TCR_amb) was determined to be 0.00312 1/K, the heater temperature, as a total dissipated power function, was extracted to 700 K at 31 mW.