Effects of Ion Bombardment on Metal-Silicon Interface

Abstract

Backscattering analysis with 1.5-MeV He ions is used to investigate the effects of Ar and As ion bombardments on thin Mo and Cr films evaporated on silicon. Ion bombardment induces the migration of metal atoms across the metal-silicon interface at room temperature. Migration is caused mainly by an atomic recoil process (knock-on effects), and not by radiation enhanced diffusion. It is also affected by the interface interaction between metal film and silicon substrate. The interface interaction is enhanced by lattice defects produced in the substrate near the interface during ion bombardment, especially in the lower dose range where lattice defects are pronouncedly created.

Migration of metal atoms depends strongly on the thickness of metal film, and occurs most noticeably when the value of the film thickness is fairly smaller than the projected range of incident ions in the metal film. Experimental results show that in the most efficient case, about four Mo-atoms are recoil-implanted into silicon by every 150-KeV Ar ion, and about ten Cr-atoms by every As ion.