A Study on Achieving Erosion-Less Depending on Pattern Density via Radical Oxidation in Copper-Film Chemical–Mechanical Planarization

Abstract

For advanced semiconductor devices, erosion and edge over erosion (EOE) after Cu-line CMP, degrading the device performance and yield, has tried indispensably to be minimized, which has been severer for scaling-down further. As a novel solution for a free of erosion and EOE, 1-step Cu-film CMP process was designed by using a Cu-bulk-film CMP performing extremely high polishing-rate via the radical oxidation on the polished Cu-film surface and following a Cu barrier metal (BM) CMP via a hindrance layer formation on the polished Cu-film surface. In Cu-bulk- film CMP, the radical oxidation was generated by the chemical reaction between hydroxide radical (OH˙) produced by a halide oxidant (i.e., periodic acid: H5IO6) and the polished Cu-film surface; i.e., a higher halide oxidant concentration in the CMP slurry led to a thicker chemically oxidized layer (i.e., Cu2O) on the polished Cu-film surface. Not only a radial oxidation via using the halide oxidant but also the decrease of the electrostatic repulsive force between the negatively charged colloidal silica abrasives and the negatively charged polished Cu-film enhanced remarkably the Cu-film polishing-rate, which was more than 2 times higher than the previous reports. To achieve an almost free of erosion and EOE, the Cu BM CMP using the slurry having both halide oxidant and inhibitor (i.e., BTA) to form the polishing-rate hindrance layer was continuously conducted just after planarizing the Cu-film surface topography through the Cu-bulk-film CMP slurry. In particular, the Cu BM slurry using 20-nm-diameter colloidal silica abrasives, the halide oxidant, and the inhibitor having amine functional group performed an almost free of erosion and EOE for all Cu-line (i.e., 100 nm in width) pattern densities. Above 1-step Cu-film CMP process would achieve an almost free of erosion and EOE although the Cu-line width scales down continuously.