Porous silicon-based humidity sensor with interdigital electrodes and internal heaters

A novel design of a one wafer side processed porous silicon-based humidity sensor with interdigital electrodes is presented. An integrated heater element over the porous layer provides the effective heating and the low power consumption of the device. Reliable contacts between metal and porous Si are formed via crystalline n-Si islands within the porous layer, formed by exploiting the selectivity of the electrochemical etching process. The effects of the electrode and heater geometry and also the parameters of the porous matrix are investigated with special emphasis on response and recovery time. To ensure the adequate thermal conditions sensor structures and packaging techniques were also investigated. The applied heater geometry results in faster recovery at a cost of reduced power consumption. (C) 2003 Elsevier B.V. All rights reserved.