Development of a production worthy copper CMP process

A chemical mechanical polishing (CMP) process for copper damascene structures has been developed and characterized on a second generation, multiple platen polishing tool. Several formulations of experimental copper slurries containing alumina abrasive particles were evaluated for their selectivity of copper to Ta, TaN and PETEOS films. The extent of copper dishing and oxide erosion of these slurries is investigated with various process parameters such as slurry flow rate, platen speed and wafer pressure. The amount of dishing and erosion is found to be largely dependent on process parameters as well as the slurry composition. It is shown that the extent of oxide erosion and copper dishing can be significantly reduced by using a two slurry copper polish process (one slurry to polish copper and another to polish barrier layers) in conjunction with an optical end-point detection system.