A wet etching system for selectively patterning substrates having regions covered with self-assembled monolayers (SAM) thereby controlling the etch profile. The system contains a) a liquid etching solution; and b) at least one additive to the liquid etching solution having a higher affinity to the regions of the substrate covered with the SAMs than to the other regions of the substrate. Also provided is a method of selectively patterning substrates having regions covered with self-assembled monolayers (SAMs), thereby controlling the etch profile, the method consisting of the steps of a) providing a liquid etching solution; b) adding at least one additive to said etching solution having a higher affinity to the regions of the substrate covered with the SAMs than to the other regions of the substrate; and c) etching said substrate with said liquid etching solution containing at least one additive.