Thermal analysis of silicon carbide based micro hotplates for metal oxide gas sensors

This paper reports on the thermal analysis of a novel micro hotplate design for metal oxide gas sensors. The hotplate is a 500 μm × 500 μm square shaped membrane made of 2 μm thick polycrystalline 3C-SiC on a silicon substrate suspended by four legs. The membrane is heated by an on chip platinum thin film heater. For reasons of a short response time and a high sensitivity a uniform temperature profile is desired. In the experiments reported here, the temperature distribution across the membrane is being measured by means of infrared thermography. To verify the absolute temperature of the thermography, reference measurements are made using an on chip platinum temperature sensor, commercially available thermal melt crayons, and K-Type micro thermocouples. The measured temperature results vary depending on the method used between 430 °C for the thermography and 870 °C with the melt crayons at a supplied heater power of 300 mW.