Sputter deposition and etching of metallization seed layer for overhang and sidewall improvement

Abstract

An integrated sputtering method and reactor for copper or aluminum seed layers in which a plasma sputter reactor initially deposits a thin conformal layer onto a substrate including a high-aspect ratio hole subject to the formation of overhangs. After the seed deposition, the same sputter reactor is used to sputter etch the substrate with energetic light ions, especially helium, having an energy sufficiently low that it selectively etches the metallization to the heavier underlying barrier layer, for example, copper over tantalum or aluminum over titanium. An RF inductive coil generates the plasma during the sputtering etching while the target power is turned off. A final copper flash step deposits copper over the bare barrier field region before copper is electrochemically plated to fill the hole. The invention also includes a simultaneous sputter deposition and sputter etch, and an energetic ion processing of the copper seed sidewall.