US Patent 7659197 Selective resputtering of metal seed layers

Metal seed layers are deposited on a semiconductor substrate having recessed features by a method that involves depositing a first portion of seed layer material, subsequently selectively resputtering the deposited seed layer material in the presence of exposed diffusion barrier material, and, depositing a second portion of the seed layer material. Resputtering operation improves seed layer coverage on the recessed feature sidewalls by redistributing seed layer material within the feature. Resputtering, however, sometimes exposes an underlying diffusion barrier material at the feature bottom and at the top corners of the feature. In order to prevent inadvertent removal of diffusion barrier layer, resputtering is performed under conditions that allow etching of the seed layer material at a rate which is at least five times greater than the etching rate of a diffusion barrier material. Selective resputtering is performed by impinging on the wafer substrate with low-energy argon and/or copper ions.