Electrochemical processes for the production of copper interconnects on non-metallic barrier layers

Abstract

This study reports the results of two process routes to eliminate the line-of-site limitations of depositing PVD copper seed layers for subsequent ECD copper deposition on nitride barrier layers. Direct deposition of adherent, low resistivity copper, directly on TaN, has been achieved using a serial electrolytic bath process. The technique uses anodic dissolution of air-formed tantalum oxides in a strong caustic bath, followed by wet transfer of wafer samples to a complexing plating bath for ECD. Highly adherent, unusually flat copper films can be produced. A second process route involves the conformal deposition of an ultra-thin plateable metallic adhesion layer on air exposed nitride surfaces, using ALD. Successful depositon of high conductivity adherent copper layers on blanket and patterned wafer surfaces has been demonstrated using Pd as a model adhesion layer.