Low-cost surface micromachined microhotplates for chemiresistive gas sensors

Microhotplate (MHP) based gas sensors have gained significant attention recently due to their small size, low power and feasibility for integration of electronics on the same chip. This study presents the detailed work on design, fabrication and complete characterization of microhotplates based on a standard multi user MEMS process (MUMPs). Suspended-membrane type MHPs were designed using the available layer combinations of MUMPs. FEM simulations were carried out to optimize the heater design by spatially varying the heater current density to achieve uniform temperature distribution over the sensing area. Topography measurements confirmed that the X–Y–Z dimensions of the fabricated MHPs were in accordance with the design. From electro-thermal characterization, the thermal efficiency of the MHPs was evaluated as ~ 10 °C/mW. The suspended membrane showed a homogeneous temperature of ~ 450 °C at 35–40 mW heater power, which was well above the typical operating temperature of chemiresistive gas sensors. The results presented in this paper provide a pathway for realizing cost effective MHPs for gas sensors based on MUMPs.