Design & Electro-Thermal Analysis of Microheater for Low Temperature MEMS based Gas Sensor

The advent of nanocrystalline metal oxide semiconductor permits microheater to be incorporated into integrated gas sensors to heat the sensing layer to a low temperature. The low temperature sensing allows the use of a relatively thin silicon membrane instead of zero Silicon membrane resulting into temperature uniformity across the entire active area (2mmx2mm) which in turn reduces the reliability problem of suspended type microheaters (on SiO2/ Si3N4 membranes) arising due to the thermal stress generated microcracks. So it is necessary to optimize the microheater design issues in order to achieve the temperature in the active area. The temperature distribution of the device sensing area of several heater configurations have been investigated here and optimized using a low cost nickel alloy DilverP1 ( alloy of Ni, Co, Fe) having high resistivity 49x10-8Ωm for micromachined silicon platform. With the new release version of COMSOL multiphysics 4.0, the user is provided a dramatic new interface from which to interact, and many new features “under the hood” for solving problems more efficiently and with even greater accuracy and consistency than before. This paper will explore several of this new version4.0 features for the temperature distribution analysis of microheater. Thermal electrical analysis was done using finite element modeling of COMSOL multiphysics 4.0. A comparative study by simulating the six different geometries namely: (a) Meander shape (b) Curved Meander shape (c) Double Spiral shape (d) Curved double spiral shape (e) S-Shape (f) Fan shape have also been presented in this paper. The device size is 5mm x 5mm with a membrane size of 2mm x2mm having an active area of 2mm x2mm and a thickness of 20μm. The maximum temperature of 473K with a distribution of ± (2-3) % over the entire microheater membrane region has been achieved with 5V excitation. A comparative study has also been made by taking different microheater element using COMSOL4.0.