| Microhotplates for metal oxide gas sensors are fabricated using platinum microheaters and tested. Power consumption is monitored and temperature distributions are observed using infrared microscopy. Temperature line traces are extracted from the resulting thermal images and compared with simulations of the microhotplates in CoventorWare 2008. Methodology for creating simulations in this software is presented. Both unreleased and thermally isolated microhotplates are fabricated and simulated. It is shown that unreleased microhotplates are ineffective in heating the microhotplate membrane, while thermally isolated microhotplates require an order of magnitude less power than unreleased devices to bring to operating temperature (300°C) for a gas sensor.;Further, CoventorWare is used to simulate microhotplates using nitrogen-doped silicon carbide microheaters, which require smaller volumes than platinum microheaters due to having higher electrical resistivity than platinum. The effects of microheater resistance and microhotplate geometry are discussed, and "coplanar" and "stacked" configurations of microhotplates resulting in uniform temperature distributions are simulated and presented. For microhotplates using a constant sensor area of 100 mum by 100 mum, the "stacked" configuration is found to be desirable because of the ability to thermally isolate a microhotplate with a smaller area, increasing the temperature attained. |
