Abstract: The present invention is concerned with etchant or etching solutions and additives therefor, a process of preparing the same, a process of patterning a substrate employing the same, a patterned substrate thus prepared in accordance with the present invention and an electronic device including such a patterned substrate. An etchant solution according to the present invention for patterned etching of at least one surface or surface coating of a substrate comprises nitric acid, a nitrite salt, a halogenated organic acid represented by the formula C(H)n(Hal)m[C(H)o(Hal)p]qC?2H, where Hal represents bromo, chloro, fluoro or b iodo, where n is 0, 1, 2 or 3, and m is 0, 1, 2 or 3, with the proviso that m+n=3; o is 0 or 1, p is 1 or 2, with the proviso that o+p=2; q is 0 or 1, with the proviso that q+m=1, 2, 3 or 4; and balance water.