Selectively deposited nickel film for via filling

A selective deposition process is used to fill vias in VLSI multilevel interconnection. Ni film is chosen as the via-filling material because of its compatibility with the underlying Al film. The vias are filled with a thin Pd film first and a thick Ni film. The deposited Ni film is uniform and smooth in the via regions. This film is not attacked by the plasma etch used in subsequent Al patterning; therefore, the design rule of overlapping the second metal on vias can be relaxed. The specific via resistance of this process is 4×10 ^-9Ω-cm². The via resistance increases about 30% after an exposure to 450°C for 8 h