title: Sol-gel zinc oxide humidity sensors integrated with a ring oscillator circuit on-a-chip.
abstract: The study develops an integrated humidity microsensor fabricated using the commercial 0.18 μm complementary metal oxide semiconductor (CMOS) process. The integrated humidity sensor consists of a humidity sensor and a ring oscillator circuit on-a-chip. The humidity sensor is composed of a sensitive film and branch interdigitated electrodes. The sensitive film is zinc oxide prepared by sol-gel method. After completion of the CMOS process, the sensor requires a post-process to remove the sacrificial oxide layer and to coat the zinc oxide film on the interdigitated electrodes. The capacitance of the sensor changes when the sensitive film adsorbs water vapor. The circuit is used to convert the capacitance of the humidity sensor into the oscillation frequency output. Experimental results show that the output frequency of the sensor changes from 84.3 to 73.4 MHz at 30 °C as the humidity increases 40 to 90%RH.
authors.affiliation: Department of Mechanical Engineering, National Chung Hsing University, Taichung 402, Taiwan. d099061005@mail.nchu.edu.tw.
authors.forename: Ming-Zhi
authors.initials: MZ
authors.lastname: Yang
authors.affiliation: Department of Mechanical Engineering, National Chung Hsing University, Taichung 402, Taiwan. cldai@dragon.nchu.edu.tw.
authors.forename: Ching-Liang
authors.initials: CL
authors.lastname: Dai
authors.affiliation: Department of Mechanical and Electro-Mechanical Engineering, Tamkang University, Tamsui 251, Taiwan. ccwu@mail.tku.edu.tw.
authors.forename: Chyan-Chyi
authors.initials: CC
authors.lastname: Wu
mesh_terms: D003217:Conductometry / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006813:Humidity; D008904:Miniaturization; D009991:Oscillometry / Q000295:instrumentation*; D044367:Phase Transition; D012666:Semiconductors; D018511:Systems Integration; D014159:Transducers; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water