A novel surface-micromachined capacitive porous silicon humidity sensor

The design, fabrication and characterisation of a novel humidity sensor are presented. The device consists of a capacitor with a porous silicon dielectric, two thermoresistors and a refresh resistor. The porous silicon is formed with a back-end process underneath a meshed metal electrode, which is fabricated in the same layer as the thermo- and refresh resistors. Due to this concept, very thin porous silicon could be formed with reproducible and stable metal contacts. At the same time, both the response time and the overall fabrication yield of the devices could be improved. The properties of the sensor are modelled and demonstrated with several experimental results.