A new method for hermeticity measurements using porous ultra low k dielectrics for sub-ppm moisture detection

A new way to detect a leakage in packaging for micro-mechanical sensors by using hydrophilic porous ultra low k dielectric components has been developed. Two synthesis means are used to deposit nanoporous SiOCH (PECVD) and MSQ (Spin Coating) with additional dedicated process to obtain high open porosity with an average pore radius distribution around 1 nm. The characterizations of the porous dielectric layers deposited on two electrodes with interdigitated fingers for capacitive measurements show a very high sensitivity to 51 % RH atmospheric air. Measurements show a 2% capacity variation for 1 ppm moisture. The process is CMOS compatible.