I. Introduction
In the recent years, intense efforts are being made to develop miniaturized gas sensors for hazardous gas detection. Especially, carbon monoxide (CO) which is a product of incomplete combustion binds with hemoglobin in the blood to form carboxyhemoglobin and reduces the oxygen-carrying capacity. As a result, vital organs such as heart, brain, and nervous tissues do not receive sufficient oxygen for their proper functioning. Long-term exposure to even low concentrations of CO also creates severe health problems to children and the fetuses of pregnant women [1]. Hence, there is a need for the development of portable and cost-effective gas sensors to detect low concentration (ppb) CO. MEMS-based metal oxide semiconductor gas sensors offer several advantages compared to optical, electrochemical techniques, such as compact size, low cost for the mass production, temperature stability, quick response and low power consumption. A high-temperature operation is needed for an optimal performance of the metal oxide semiconducting gas sensors and such temperatures can be achieved by microheaters.