Wet chemistry

Following lithography, the structures in the photoresist are transferred into the layer below by wet- or gasphase etching. It simplifies processing, if the etch process can stop on an etchstop layer below the layer to be etched, which is not attacked by the chemistry.

The second important task for wet chemistry is the cleaning of surfaces before all high temperature process steps. As impurities diffuse very rapidly at elevated temperatures, the cleanliness is extremely important for high quality processing.