Abrasive-free processes for the Cu damascene CMP process

The abrasive-free slurry approach relies on modification of the Cu-oxide layer to a copper complex layer with different chemical and mechanical properties that facilitate removal without assistance fi om abrasives. The abrasive-free polishing solutions are complex, and optimization requires understanding the impact of each component (oxidizer, complexing agent, corrosion inhibitor, and pH adjustor) on the Cu-complex formation and defectivity. 

Several abrasive-free formulafions were developed for planarizing and clearing copper films and stop on the underlying barriCT films with minimal dishing and erosion. 

US Patent 6562719 (Kondo) further describes the use of ethanol, isopropyl alcohol, ethylene glycol, and methyl ethyl ketone in abrasive-ffee polishing compositions that do not contain abrasive. These compounds were added to increase the solubility of benzotriazole (BTA), an inhibitor. 

The data suggest that chemical rather than mechanical effects dominate the removal of Cu surface layers in this system. The Cu removal efficiency of this slurry can be controlled by adjusting its acidity and H2O2 content. 

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