Methods for etching a less reactive material in the presence of a more

Abstract

A method is described for providing a body of first material and a body of second material in a chemical environment wherein the first material contains first constituents having a lower and higher oxidation state and wherein the second material contains constituents having an oxidation state of energy greater than lower oxidation state of the first constituent. The environment is further provided with first cations energetically disposed for receiving electrons from the first constituents but not energetically disposed for receiving electrons from the second constituents. Electrons transfer from the first constituents to the first cations which are transformed thereby into second cations of lower oxidation state resulting in first body releasing into the environment third cations which are cations of the first (lower) oxidation state of the first constituent. The environment is further provided with an agent which consumes the second and third cations thereby permitting release into the environment additional ones of the third cations resulting in the first body being preferably etched with respect to the second body. The method is useful to etch copper in the presence of more highly reactive materials such as chrome, lead, tin, titanium, aluminum, iron, cobalt, and galvanically more active gold and nickel. The method is useful for forming structures containing copper having an overlying layer of the more highly reactive material without the requirement of the use of a resist material.