PURPOSE: To provide a humidity sensing element which can be used continuously for a long time without requiring any complex circuit by forming on a silicon wafer such polyimide resin the capacity value of which varies much with relative humidity and reverts to its initial value even if the resin is left in high- humidity atmosphere at high temperatures for a long time and then returned to a low-humidity state.
CONSTITUTION: An ohmic contact electrode 1 is formed on the reverse face of an N-type silicon wafer 2. Polyimide resin is applied to the surface of the silicon wafer and dried and a solvent is removed therefrom and then the resin is heated and hardened to form a polyimide humidity-sensing film 3. The polyimide resin is soluble in an organic polar solvent obtained by the polymerization and formation into imide of a biphenyl tetracarbon acid group and an aromatic diamine group. Then an upper electrode 4 is formed and a semiconductor substrate is cut into an opening of chip size 5mm in diameter and upper and lower electrode takeout lead wires 5, 6 are attached to the respective portions of the substrate.
KANEBORI MASASHI
JAPAN RES DEV CORP
YAMAMOTO TATSUO
Next Patent: MANUFACTURE OF HUMIDITY SENSING ELEMENT