Abstract: The present disclosure describes a method for forming metallization layers that include a ruthenium metal liner and a cobalt metal fill. The method includes depositing a first dielectric on a substrate having a gate structure and source/drain (S/D) structures, forming an opening in the first dielectric to expose the S/D structures, and depositing a ruthenium metal on bottom and sidewall surfaces of the opening. The method further includes depositing a cobalt metal on the ruthenium metal to fill the opening, reflowing the cobalt metal, and planarizing the cobalt and ruthenium metals to form S/D conductive structures with a top surface coplanar with a top surface of the first dielectric.

Abstract: The present invention is to provide an etching solution capable of effectively reducing Galvanic effect, wherein the etching solution is obtained by way of dissolving an etchant and a nitrogen containing five-member heterocyclic compound in water. Thus, when at least one first metal (e.g., gold) and at least one second metal (e.g., copper) disposed on a substrate is treated with a wet etching process by using this etching solution, the nitrogen containing five-member heterocyclic compound would form an organic protecting film on the first metal having higher reduction potential, so as to effectively avoid the second metal from being over etched resulted from the Galvanic effect.