Low Power Consumption Microheater Platform Integrated Gas Sensor Design Using Anodic Aluminum Oxide Template

Abstract

Demands for detecting and monitoring hazardous, toxic, and flammable gases are increasing in both of industrial and domestic environments. Among various types of gas sensor, the semiconductor gas sensors are promising candidate for gas monitoring platforms due to high performances and low cost [1]. The semiconductor gas sensors use conductometric change by redox reaction between oxygen ions and target gases, which requires high temperature. Microheater platforms have been researched to get high performance semiconductor gas sensors [2] However, the microheater platforms form suspended structures to reduce heating power consumption, which reduce long-term stability. Nanoporous anodic aluminum oxide (AAO) has low heat conductivity and high thermal efficiency due to nanoscale air pores [3]. In this paper, microheater integrated gas sensor based on anodic aluminum oxide template is designed for low power consumption and high-performance gas sensing. The microheater integrated AAO based gas sensor was designed and verified using FEM simulation. The AAO template was fabricated by two-step anodization for uniform nanopoorous structure [4]. Conventional lithography process could not be applied due to nanopores, additional metal layer was deposited for micro-scale patterning. Air gap patterns were fabricated by AAO etching with a high aspect ratio to reduce heating power consumption. The tungsten trioxide as a sensing layer was deposited by glancing angle deposition (GLAD). The heating power consumption of the fabricated microheater platform was controlled to 16mW, and the temperature was about 250℃. Tungsten trioxide deposited by GLAD formed nanodot structures on the vertices of AAO surface. Nanodots increase surface area of the sensing layer, thereby high sensitivity to target gas. The gas sensing properties of WO3 on AAO template showed extremely high response to NO2 gas exposure (Rgas/Rair = 274).