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.
The wafers can be etched on one side. (Spin etcher SEZ102) the underside of the wafer is covered by a protected nitrogen bed from the etching.
The wafers can also be etched on both sides. (Spray etching system)
Automatic wet bench (RCA sequence with a total of 7 pools)