Patent ID: 7850866

Claim:
An etchant, comprising: a first concentration of hydrogen peroxide (H 2 O 2 ) for oxidizing Mo and Cu; a second concentration of sulfuric acid (H 2 SO 4 ) for reacting with the oxidized Cu; and a hydrogen peroxide (H 2 O 2 ) stabilizer, wherein respective amounts of the first and second concentrations are such that the etchant is capable of simultaneously etching a double-layered metal layer, which includes a copper (Cu) layer on a molybdenum (Mo) layer, to form a double-layered metal line having the molybdenum layer extending outwardly from underneath an edge of the copper layer, wherein the sulfuric acid (H 2 SO 4 ) has a weight percent of 5 wt %, and wherein a molar ratio of hydrogen peroxide (H 2 O 2 ) to sulfuric acid (H 2 SO 4 ) is between 1 and 3.