  At the Department of Electron Devices a cheap, more or less CMOS process
compatible capacitive type RH sensor has been developed. Capacitive sensors are
based on dielectric property changes of thin films upon water vapour uptake
which depends on the surrounding media's relative humidity content. Because of
the immense surface-to-volume ratio and the abundant void fraction, very high
sensitivities can be obtained with porous ceramics. One of the ceramics to be
used is porous Al2O3, obtained by electrochemical oxidation of aluminium under
anodic bias. The average pore sizes are between 6...9 nm. In our paper we
intend to demonstrate images representing the influence of the technological
parameters on the porous structure and the device sensitivity.
