Device and method of manufacturing a relative humidity sensor and temperature sensor

Abstract

Sensor and method of fabricating a sensor for detecting relative humidity with a substantially linear response from 0% to 100% and also detecting temperature. The sensor utilizes a unique essentially pure Al.sub.2 0.sub.3 layer which has a disordered crystalline structure and a density gradient which varies from a low density at its lower surface to a higher density at its upper surface which together produce the desired linear response to relative humidity. The method of producing the unique essentially pure Al.sub.2 O.sub.3 layer includes anodizing with an ac current in a solution of approximately 6.4 normal acid at a starting temperature of 21.degree. C. and allowing the temperature of the anodizing solution to rise with the process to vary the density of the Al.sub.2 O.sub.3 layer. The Al.sub.2 O.sub.3 layer is neutralized in a base solution, washed in boiling water and alcohol to neutralize the Al.sub.2 O.sub.3 layer and remove impurities. The sensor is employed as a three-terminal semiconducting device which is biased with dc current, allowing implementation with standard ICs and LSI circuitry. Application of a biasing current on the top electrode allows the RH sensor to be operated simultaneously as a temperature sensor.

Dependencies are inferred from the claim text.