Thermally/mechanically robust anodic aluminum oxide (AAO) microheater platform for low power chemoresistive gas sensor

Abstract

The semiconductor metal oxide (SMO) gas sensors are getting high attention owing to their high sensitivities and fast responses. They require high temperature for the reaction with target gases, and suspended silicon membrane microheaters are typically used to reduce the heating power consumption. However, they have low durability for long-term uses, and high probability of fracture by thermal stress or mechanical impact. In this study, as an alternative to the silicon membrane microheater, anodic aluminum oxide (AAO) based microheater platform gas sensor was fabricated for low power consumption and high thermal/mechanical stabilities. Nanoscale air gaps of the AAO substrate reduce the heat loss transferred to the substrate. Therefore, AAO-based microheater platforms do not require suspended structures sustained by very thin bridges, which dramatically enhances thermal/mechanical stabilities. The temperature of fabricated microheater platform reached to 250℃ by a heating power of 27.4 mW. The excellent thermal/mechanical stabilities of the AAO-based microheater platforms were verified by cyclic on-off and mechanical shock test. The pulsed heating operation was adopted, and it reduced the heating power consumption to 9 mW. The fabricated AAO-based gas sensors showed much higher responses to NO2 gas compared to the SiO2 membrane-based gas sensors.

Development of a Microheater with a Large Heating Area and Low Thermal Stress in the Heating Area

“…The mechanical stability of the multilayer membrane structure was tested, and it was found that the center of the microheater deflected more than a few micrometers after heating the microheater plate to a temperature of 350 K. When the microheater was heated to 550 K, the amplitude of the center of the microheater exceeded 30–40 μm. Byeongju Lee et al [ 20 ] prepared an anodized aluminum oxide-based microheater that fabricated a bridge structure with the same thickness as the substrate using the etching mechanism of the anodized aluminum oxide substrate. Because the heating platform uses the entire thickness of the substrate instead of a microscale membrane, the microheater platform has exceptional mechanical and thermal stability.…”