Over 90% Reduction of Response Time in Flexible MEMS Thermal Sensor Using Localized Backside Laser Ablation

Thermal sensing in MEMS has great potential for developing flexible physical sensors due to the absence of resonating structures. However, achieving fast response times requires minimizing thermal mass around the sensing element. Unlike rigid MEMS sensors, flexible sensors face significant challenges in fabricating free-standing structures due to their lack of mechanical support. Traditionally, reducing thermal mass has been achieved by using thinner substrates, but this approach was limited by handling and installation difficulties. To overcome this, here we propose a laser ablation technique to selectively remove unnecessary substrate material from the backside of flexible MEMS thermal sensors. Using a pulsed UV laser, localized ablation effectively reduces thermal mass, leading to a significant improvement in response time. Experimental validation through thermal analysis and airflow sensor testing confirmed that this approach successfully suppressed time response by over 90%.