Anodic aluminum oxide-based capacitive humidity sensor integrated with micro-heater

, , , , , ,

Keywords: , ,

AAO(Anodic Aluminum Oxide) film is fabricated as a sensing material of capacitive humidity sensors. Because AAO films have a lot of nano-size pores, many water vapors can be absorbed. The size of a pore diameter is 80nm. Rectangular spiral-shaped type and interdigitated type are designed and fabricated as electrode types. A micro heater is also integrated because condensed water vapors and contaminants should be evaporated. Using heater, we can improve linearity and reliability and we can reduce hysteresis largely. As a porous layer thickness increases, a sensitivity become higher. That means a thick porous layer can absorb more water vapors. But a response time also increases as a porous layer thickness increases. A sensitivity of rectangular spiral-shaped type is higher than that of interdigitated type. And a response time of rectangular spiral-shaped type is faster than that of interdigitated type. But a hysteresis is independent of electrode type. The experiment using heater shows a good linearity with a small hysteresis for the relative humidity. The condition is the interdigitated type with a 50 porous layer under the electric power of 7v(749mW) . Under this condition, we don’t need a additional linear modification.

PDF of paper:

Journal: TechConnect Briefs
Volume: Technical Proceedings of the 2008 Clean Technology Conference and Trade Show
Published: June 1, 2008
Pages: 658 - 661
Industry sectors: Energy & Sustainability | Sensors, MEMS, Electronics
Topic: Chemical, Physical & Bio-Sensors
ISBN: 1-4200-8502-0