| 摘要 |
PURPOSE:To make it possible to drive with low electricity consumption and low voltage a gas sensor element that has a thin film solid electrolyte at the gate section of a MOS type FET construction and improve response time and reliability by applying the driving voltage with a pulse wave form symmetric with respect to both plus and minus. CONSTITUTION:A gas sensing element of MOS type FET construction is formed by providing a grid-mesh type metallic electrode 6 on n type source, drain 2, field oxide 3, metallic gate electrode 4 and solid eleactrolyte 5 on a P type Si wafer 1. One of LaF3, CeF3, NaF3, and PrF3 is selected as the solid electrolyte layers. A thin film battery construction is thus formed with the electrode 6/solid electrolyte layer 5/ electrode 4. When the element is exposed to a gas in the environment with a given voltage (for example, 250 WV for O2 gas and 50WV for NO gas) applied between the electrodes 4 and 6, current flows between them and the voltage of the electrode 6 works as the gate voltage. After sensing reversed voltage of the shape equivalent to that of sensing is applied to the electrode in order to return it to the state right before the sensing to use it again. |
