Design and electrothermal analysis of MEMS based microheater array for gas sensor using INVAR alloy

Most of the microheaters, which are used to elevate the temperature of gas sensor, integrated with the design of either platinum, nichrome or polysilicon as heater element suitable for high temperature (400-700°C) regime. This paper describes the structural design and electrothermal analysis of a microheater array to find out the thermal characteristic with different bias voltages. The standard meander shaped microheater was designed using a Fe, Ni, Co alloy (Invar) having lower thermal expansion coefficient (~3×10^-6/ °C) and thermal conductivity (~10.4W/M-K) and high resistivity (~80×10^-8Ωm). The array consists of four unit cell, each of 3mm × 3mm of dimension with a membrane size of 1.5 mm × 1.5 mm. This device has the unique advantage of making the microheater and interdigitated electrode co-planner using a single lithography process. The maximum temperature of ~212°C was achieved with 4.5V excitation with lower power consumption of ~90mW. Invar alloy offered very good temperature uniformity in the active region with tolerance of ~1%.