| 摘要 |
1416315 Humidity transducers OMRON TATEISI ELECTRONICS CO 9 Nov 1972 [10 Nov 1971 21 March 1972] 51837/72 Heading G1N [Also in Division H1] Humidity is sensed in terms of the current passed by a reverse biased rectifying interface between a tin oxide film and a semi-conductor body on which it is deposited directly or through the intermediary of a thin insulating film, when the interface is exposed to the humidity to be sensed. Suitable materials are silicon, germanium and gallium arsenide for the semi-conductor body and silica, silicon nitride and germanium dioxide for the optional insulating film. A preferred device based on a lohm. cm. N type silicon wafer 200Á thick comprising a 15-500 A silica layer and a layer of tin oxide 6Á thick is made as described in copending application 51836/72 up to completion of the tin oxide layer, which is then coated with nickel by vapour deposition. The oxide on the periphery of the wafer is then exposed by etching away the overlying nickel and tin oxide, and removed by treatment in 5% hydrofluoric acid. A natural oxide layer which reforms on the exposed surface may be reinforced. If the device is required to be light-sensitive an area of the nickel overlying the transparent tin oxide is removed. The reverse breakdown voltage of the interface increases with increasing humidity. In operation with the interface biased beyond its breakdown voltage the avalanche current decreases with increase in humidity.
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