Patent ID: 8617997

Claim:
A method for fabricating an electronic device using selective wet etching, the method comprising: providing at least one wafer comprising at least one first surface; depositing at least one first layer comprising solder material adjacent to the at least one first surface, wherein the solder material comprises composite AuSn; depositing at least one second layer comprising etch mask material on said at least one first layer comprising solder material; introducing a plurality of liquid etching compositions to the at least one first layer comprising solder material, each of said plurality of liquid etching compositions comprising a different chemical composition, said plurality of liquid etching compositions introduced in a repeating, alternating fashion; and etching the at least one layer comprising solder material for a period of time sufficient to selectively etch at least one portion of the at least one solder layer with the plurality of liquid etching compositions; wherein selective wet etching is achieved using a wet etch process comprising: introducing the at least one first layer to at least one composition comprising at least one of HF, HCl and HNO 3 ; and introducing the at least one first layer to at least one composition comprising aqua-regia.