TEM analysis of microheater using SiO2/Si3N4 composite membrane for long term gas sensing applications

In this paper, simulation result of MEMS based micro-hotplate using the finite element method (FEM) has been presented. FEM subdivides a large problem into smaller, simpler parts, called finite elements. The electro-thermo-mechanical behaviors of micro-hotplates have been simulated using INTELLISUITE 8.2.2 software. A composite membrane (SiO
₂
/Si
₃
N
₄
) was used in this case in order to obtain a stress compensated structure to achieve the long term stability of gas sensor. A low cost material, nickel having resistivity of 6.8 ohm.m is used as a heating element. Temperature of the micro-heater, displacement of the membrane and power consumption of the micro-hotplate is evaluated. Results show that the thickness of the heating element if increased from 0.25, temperature increases from 144°C to 624°C for SiO
₂
/Si
₃
N
₄
composite membrane whereas it increases from 129°C to 535°C for SiO
₂
membrane with 5V excitation. Simultaneously, displacement (1.52μm to 1.87 μm) and stress (47.28MPa to 211.38MPa) are also studied with the increase in thickness of the heating element (0.25 to 1 μm) with 5V excitation. All the simulations are valid for complete metal oxide gas sensor using ZnO sensing layer.