Method of electrodepositing gold on a copper seed layer to form a gold metallization structure

A method of forming a gold metallization structure by electrodeposition using a copper seed layer, the method comprising:

• forming an electrically conductive barrier layer covering a surface of a semiconductor substrate, the substrate comprising a source and drain terminal of a semiconductor device, such that a continuous portion of the barrier layer contacts the source and drain terminals;
• forming a copper seed layer such that a continuous seed layer portion covers the continuous portion of the barrier layer;
• masking the seed layer with a mask having first and second openings that are laterally aligned with the source and drain terminals;
• electroplating unmasked portions of the seed layer using a gold electrolyte solution so as to form first and second gold metallization structures arranged in the first and second openings;
• removing the mask;
• removing the masked portions of the seed layer and the barrier layer so as to electrically isolate the first and second gold metallization structures;
• and
• diffusing copper atoms from the seed layer into the first and second gold metallization structures,
• wherein the first and second gold metallization structures are electrically connected to the source and drain terminals, respectively, and
• wherein diffusing the copper atoms comprises diffusing all metallic state copper from the unmasked portions of the seed layer into the first gold metallization structure such that gold from the first gold metallization structure directly contacts the barrier layer.