A bulk micromachined humidity sensor based on porous silicon

This paper reports on the development of a micromachined membrane humidity sensor. The sensor utilises the capacitance technique to measure relative humidity. The membrane, which acts as the dielectric, is made porous using a standard anodisation technique. The advantages of this type of construction compared to the standard bulk-type sensor are outlined. Also, a heating resistor is incorporated underneath the membrane. This acts as a reset to the device by driving out excess moisture.