Abstract
The fabrication of a nanowire WO 3 humidity sensor integrated with an inverting amplifier circuit and a micro-heater on a chip using the commercial 0.35 μm complementary metal oxide semiconductor (CMOS) process and a post-process have been implemented. The humidity sensor is composed of a sensing resistor and a humidity sensing film. Tungsten trioxide prepared by a sol-gel method is adopted as the humidity sensing film. The fabrication of the humidity sensor requires a post-process to etch the sacrificial layers and to expose the sensing resistor, and then the humidity sensing film is coated over the sensing resistor. The humidity sensor, which is a resistive type, changes the resistance when the sensing film adsorbs or desorbs water vapor. An inverting amplifier circuit is utilized to convert the resistance of the humidity sensor into the voltage output. The micro-heater is utilized to provide a super-ambient working temperature to the humidity sensor, which can avoid the humidity sensor to generate the signal drift. Experimental results show that the sensitivity of the humidity sensor is about 4.5 mV/% RH at 60 °C.
| Original language | English |
|---|---|
| Pages (from-to) | 896-901 |
| Number of pages | 6 |
| Journal | Sensors and Actuators, B: Chemical |
| Volume | 123 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published (in print/issue) - 21 May 2007 |
Funding
The authors would like to thank National Center for High-performance Computing (NCHC) for chip simulation, National Chip Implementation Center (CIC) for chip fabrication and the National Science Council of the Republic of China for financially supporting this research under Contract No. NSC 95-2221-E-005-043-MY2. Ching-Liang Dai received the MS degree in the applied mechanics from National Taiwan University, Taiwan, in 1993, and the PhD degree in the mechanical engineering from Nation Taiwan University, in 1997. He is currently an associate professor at the Department of Mechanical Engineering, National Chung Hsing University, Taiwan. His research interests are CMOS-MEMS, integrated microsensors and RF MEMS. Mao-Chen Liu received the MS degree in the precision engineering from National Chung Hsing University, Taiwan, in 2004. He is currently a candidate for doctor's degree at the Department of Mechanical Engineering, National Chung Hsing University, Taiwan. His research interests are semiconductor sensors, analog circuits and radio frequency circuits. Fu-Song Chen received the BS degree in the mechanical engineering from National Chung Hsing University, Taiwan, in 2004, and the MS degree in the precision engineering from National Chung Hsing University, in 2006. His research interests are gas sensors and micro-actuators. Chyan-Chyi Wu received the PhD degree in the mechanical engineering from National Taiwan University, Taiwan, in 2001. He is currently a researcher at Industrial Technology Research Institute, Taiwan. His research interests are optical physics, biophysics, optical interferometry and near-filed/far-field microscopy. Ming-Wei Chang received the BS degree in the mechanical engineering from Huafan University, Taiwan, in 2000 and the MS degree in the mechatronics engineering from Huafan University, Taiwan, in 2002. He is currently an engineering researcher and an advanced project leader at the RFID center, Industrial Technology Research Institute, Taiwan. His research interests are micromachined transducers and Bio-MEMS.
Keywords
- CMOS
- Humidity sensor
- Inverting amplifier circuit
- Micro-heater
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