PRT Embedded Microheaters for Optimum Temperature Distribution of Air-Suspended Structures for Gas Sensor Applications

Abstract

Presently, a lot of research effort has been directed toward the development of small dimensional gas sensing devices, based on metal oxides, for practical applications ranging from toxic gas detection to pollution monitoring in the air ambience. The demand for better environmental control and safety has increased research activities of microgas sensors and their development. For this purpose, MEMS-based sensors in the form of thin or thick films seem to be more promising. Metal oxide-based sensors work on the principle of electrical conduction variation and for this purpose a predetermined temperature is crucial for the sensing films for best sensitivity values. Creating correct temperature and the proper temperature distribution is of paramount importance for these sensors. Creating thin film platforms for this purpose is crucial and practically limits the yield. This paper presents the results obtained for thick air-suspended platform, using ANSYS, for a PRT (platinum resistance thermometer) embedded microheater that is suitable to operate by a dc battery source. Both the microheater and PRT were defined in a single photolithography step and are realized on an oxidized silicon substrates (SiO2/Si). Realistic values are used to simulate the data and to obtain the optimum temperature distribution, of the order of 400 °C, over an area of 5 mm × 4 mm of air-suspended platform. These studies help greatly to visualize the microheater design to help in understanding the heat distribution on the membrane, where the sensing layer will be placed and also to get the optimum sensing properties of microgas sensors. Using embedded PRT, it is easy to confirm and control the required temperature necessary for the sensing layer. This approach simplifies the process to achieve a simple and practical device.