Apparatus and method for stopping an etching process

A method for etching a layer assembly which includes an intermediate layer (120) between an etch layer (110) and a stop layer (130), said method comprising the steps of: Etching the etch layer (110) using a first etchant, wherein the first etchant comprises a first etch selectivity with respect to the etch layer (110) and the intermediate layer (120); and Etching the intermediate layer (120) using a second etchant wherein the second etchant has a second etch selectivity with respect to the intermediate layer (120) and the stop layer (130), wherein the second etchant different than the first etchant.