Laser Ablation for Time Response Suppression of Flexible MEMS Thermal Sensors

Thermal sensing mechanism in microelectro mechanical system (MEMS) has an inherent potential to realize various flexible physical MEMS sensors due to the absence of resonating structure. In such thermal sensors, it is crucial to limit the thermal mass around the sensing structure to speed-up the time response. The absence of rigid body presents technical challenges to fabricate free-standing sensing elements in flexible MEMS sensors. In such sensors, the thermal mass has been generally limited by the utilization of thin substrates. However, there is a limit when switching to thinner substrate becomes challenging, mainly due to handling and installation constraints. As a solution, here we propose a laser ablation process to locally remove the unnecessary substrate parts in flexible MEMS thermal sensors. The concept was validated experimentally through thermal analysis and response time measurements under operation as airflow sensors. Time response suppression of up to 50% was confirmed.