Method for patterned etching of selected material

A method of etching an unmasked exposed uniform surface of a material layer, wherein the etching is restricted to an etch pattern area on the unmasked exposed uniform surface, the etch pattern area extending over only a part of the unmasked exposed uniform surface, the method comprising:

• (a) providing at least a first component required for the etching of the material layer as a surface layer extending over a region of the unmasked exposed uniform surface of the material layer to be etched, the surface layer covering at least the etch pattern area and the surface layer being applied using one of a flow-on method, a spin-on method, a spray coating method or a printing method;
• (b) providing at least one deposition composition comprising one or more further components required for the etching of the material layer;
• and
• (c) applying the at least one deposition composition over the region of the unmasked exposed uniform surface to be etched in a pattern corresponding to the etch pattern area;
• whereby the first component required for etching the material layer reacts with the one or more further components required for etching of the material layer to form an etchant to etch the material layer only in the etch pattern area.