Dependency of dishing on polish time and slurry chemistry in CuCMP

In this paper the influences of slurry chemistry and thickness of the coppe r layer on dishing will be discussed. The dishing is studied for different patterns and variable polishing times. We found that the concentration of t he oxidiser and the thickness of copper layer have a strong impact on dishi ng. The larger Cu features develop dishing at a higher rate than smaller st ructures during overpolishing. The experimental results lead to the followi ng hypothesis for the Cu removal and surface passivation. The oxidizer (H2O 2) reacts with Cu in an acidic slurry (pH 4) and Cu2+ ions are formed. The anions of the carboxylic acid react with Cu2+ ions and form an insoluble sa lt (R(COO)(2)Cu) which passivates the surface. This passivation layer is re moved in protruding areas by mechanical abrasion. Once removed from the sur face, the 'metallic soap' particles are swept away by the turbulent motion in the slurry. (C) 2000 Elsevier Science B.V. All rights reserved.