Abstract
A method for forming a metal film with twins is disclosed. The method includes: (a) forming a metal film over a substrate, the metal film being made of a material having one of a face-centered cubic crystal structure and a hexagonal close-packed crystal structure; and (b) ion bombarding the metal film at a film temperature lower than -20.degree. C. in a vacuum chamber and with an ion-bombarding energy sufficient to cause plastic deformation of the metal film to generate deformation twins in the metal film.