| Summary: | 碩士 === 國立中興大學 === 精密工程研究所 === 92 === This study investigates the fabrication of a gas sensor using the TSMC .35 2P4M standard process. The structure of the gas sensor contains the N and P type poly-silicon series and a sensing film. The N type layer deposit the oxide layer and the P type layer coats the sensing layer. The sensing layer is SnO2, which is deposited by Sol-Gel method.
Using the Sol-Gel method can fabricate many gas sensors especially to CO sensor. The sensing layer contacts air in junction produced the Schottky barrier. When the sensing layer adsorbs gas molecule, the Schottky barrier will to decrease. Because the absorbtion effect reduces the Schottky barrier. The resistance of the sensing layer decreases. When SnO2 layer absorbs gas molecule, The resistance of the P type poly-silicon increases. Beacuse the SnO2 and P type poly-silicon's heterojunction and the air and SnO2 contacts, these junction's enery band will equilibrium and interrelationship to make resistance change. Using this way to detect the gas can integrate the SnO2 layer and the standard IC process. If the gas sensor only uses the SnO2 layer, without P and N type poly-silicon the resistance will change very violent to outstrip million ohm. The method is easy to combine with IC desig
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