Effects of BF2+ implantation on the oxidation resistance of copper films

Abstract

This work investigates the effects of BF2+ implantation on the oxidation resistance of copper films. The BF2+ ions were implanted into Cu films through a 1000 Angstrom thick screen SiO2 layer. We found that the oxidation resistance of Cu films can be significantly improved by BF2+ implantation at appropriate conditions. In particular, BF2+ implantation at 35 to 40 keV to a dose of 1 - 8 x 10(14) cm(-2) made the Cu films capable of resisting oxidation at temperatures up to 250 degrees C. At these BF2+ implantation energies, boron atoms of peak concentration were projected near the Cu surface; thus the diffusion paths of oxidizing species were efficiently blocked. Implantation at too high energy would result in greater depth of projection, thus a lower concentration of boron at the Cu surface; moreover, it generally leads to increased implantation defects that might serve as diffusion paths for the oxidation species. On the other hand, too high dosage implantation would also have an adverse effect on the capability of oxidation resistance for Cu films owing to the higher density of implantation damage as well as the formation of reactive fluorine compound (CuF2) near the Cu surface. (C) 1999 Elsevier Science S.A. All rights reserved.