US Patent 9905670 Bi-layer metal deposition in silicide formation

A method includes performing a first sputtering to form a first metal film on a surface of a semiconductor region. The first sputtering is performed using a first ion energy. The method further includes performing a second sputtering to form a second metal film over and contacting the first metal film, wherein the first and the second metal films includes a same metal. The second sputtering is performed using a second ion energy lower than the first ion energy. An annealing is performed to react the first and the second metal films with the semiconductor region to form a metal silicide.