Design and Electrothermal analysis of MEMS based Microheater Array for Gas Sensor using INVAR alloy 1 * 2 2 S.S.Mondal , S.Roy , C.K.Sarkar I Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata- 700032, India 2 IC Design and Fabrication Center, Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata- 700032, India * Corresponding author: Tel.: +913324146217 *E-mail: subrata.3010mail.com Abstract - 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 ind 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 coeicient (-3xl0- 6 / 0c) and thermal conductivity (-10.4W/M-K) and high resistivity (-80xl0- 8 Qm). The array consists of four unit cell, each of 3mm x 3mm of dimension with a membrane size of 1.5 mm x 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 %. Keywords- MEMS, INVAR Alloy, Thermal expansion coeicient, Coplanar. I. INRODUCTION Microheater array is the generic structure of different numbers of heater combined and it can be designed to detect the individual gases from a mixture of true gases by coating with different sensing ilms at a certain time with its different sensor block devices [1,2]. The sensing ilms are generally oxide or metal oxide compositions and 978-1-4673-4700-6/12/$31.00 ©2012 IEEE 468 allow for the determination of information about the ambient gases [3,4]. The required temperature for the gas sensor is generally (-ISO-300°C) as these temperatures provoke many factors related to the sensing ilm generally semiconducting metal oxides (ZnO,Sn02 etc.) and plays a signiicant role in determining the response to the target gases like CH4, CO, N02 etc.[5-7]. Microheaters generate optimum operating temperature for different semiconducting metal oxides. So microheater array is more suitable than a single microheater for gas sensor devices. Micro-electromechanical systems (MEMS) based integrated gas sensors provide several advantages for applications such as array fabrication, small size, and unique thermal manipulation capabilities, uniform heating throughout the active area [8] . Roy et.al.[9] has already discussed elaborately the signiicance of co-planar structure with microheater and IDE produced by a single lithographic step on micromachined silicon substrates using a novel nickel alloy DilverP1 with its advantages over other heating elements. The larger coeicient of thermal expansion (CTE) may have contributed to the deformation of the microheater shape during temperature rise. Moreover the lower thermal conductivity enhances the coninement of the temperature within the active region supporting low power consumption. Keeping these in mind Invar alloy has been proposed in this paper as a microheater as well as electrode element ment with lower CTE, young modulus, lower thermal conductivity and micro yield strength [10] and presented as the meander shaped microheater as well as electrode element for micromachined metal oxide based gas sensor devices. IDE supports the increased sensitivity of the sensing ilm by utilizing the maximum sensing area.