Dishing-free chemical mechanical planarization for copper films

Abstract

The importance of obtaining a dishing-free Cu-film chemical-mechanical planarization (CMP) has rapidly increased as the line width of Cu-wire integration in advanced semiconductor devices reduced to less than 10 nm. Unlike conventional etching (i.e., corrosion) dominant Cu-film CMP, which has been utilized for the last two decades, a novel chemical oxidation and etching dominant Cu-film CMP using a slurry performing Fenton reaction between a ferrous catalyst (Fe(CN)64?-) and oxidant (H2O2), a scavenger (arginine) effect, and the enhanced mechanical property of a nano-scale (i.e., 20 nm in diameter) crystalline ZrO2 abrasive could successfully obtain a dishing-free Cu-film CMP and good stability of abrasives in the slurry. In particular, the Cu-film polishing rate significantly increased with an increase in ferrous catalyst and scavenger concentrations; a 12-inch-wafer Cu-film polishing rate of >220 nm/min was obtained at a ferrous catalyst concentration of 2.0 wt% and a scavenger concentration of 1.0 wt%. Otherwise, the SiO2-film polishing rate significantly decreased with increasing ferrous catalyst and scavenger concentration. The dependencies of the chemical properties (i.e., static etch rate, surface chemical compositions, and corrosion) and mechanical properties (i.e., electrostatic force) proved that the CMP mechanism using Fenton reaction and the scavenger effect principally perform chemical oxidation (i.e., the formation of CuO and Cu2O on the Cu film surface) and etching dominant CMP simultaneously.