Cu deposition characteristics into submicron contact holes employing self-sputtering with a high ionization rate

Cu deposition profiles in submicron contact holes are investigated employing the Cu self-sputtering which do not need any inert gas e.g. Ar during sputtering. Excellent bottom coverage in the high aspect ratio contact holes was obtained at a large target-substrate distance in the self-sputtering due to a long mean free path of Cu ions and atoms, although a coverage is poor in Ar sputtering at 6 mTorr. It is also shown that the self-sputtering has low resputtering effect and high self-diffusivity of Cu, while the resputtering predominates in the case of Ar sputtering when DC bias is applied on the substrate. As a consequence, the bottom coverages of the self-sputtered films are much improved than the Ar sputtered ones. The present work strongly suggests that the self-sputtering is promising to fill Cu in sub micron via and contact holes.