Effect of Under-Layer Treatment of Ta/TaN Barrier Film on Corrosion Between Cu Seed and Ta in Chemical-Mechanical-Polishing Slurry

Abstract

Tantalum/tantalum nitride (Ta/TaNx) composite film is widely used as a copper (Cu) diffusion barrier layer. In order to reduce via-resistance, an additional argon (Ar) re-sputtering process is used to thin the barrier thickness at the feature bottom. In this study, the effect of Ar re-sputtering of the under-layer of TaNx barrier films on the corrosion between Cu seeds and upper Ta films in chemical-mechanical-polishing (CMP) slurries was investigated. The results show that Ar re-sputtering of the under-layer of the TaNx barrier has a strong influence on the corrosion of Cu seeds and Ta films. The equivalent circuit, simulated using data from electrochemical analysis, reveals changes in resistance and capacitance elements of the Cu-Ta electrochemical system, proving that the phase transformation of upper Ta films under different TaNx conditions leads to different degrees corrosion of Cu seeds and the Ta films.

Effect of Chelating Agent and Surfactant on TaN CMP in Weakly Alkaline Slurry

“…2 Chemical Mechanical Planarization (CMP) is one of the key processes for IC fabrication, and the only way to achieve global and local planarization.The CMP for TaN chemical behavior has been investigated by many researchers. [3][4][5][6][7][8] S. V. S. B. Janjam 9 studied the TaN removal rate (RR) up to 100 nm /min in solutions using oxalic and tartaric acid as chelating agent and H 2 O 2 as oxidizer. Meanwhile, they also investigated the electrochemical behavior of TaN in solutions of H 2 O 2 and tartaric acid, 10 indicating that the Ta sites of TaN were oxidized to Ta 2 O 5 by O 2 and H 2 O 2 in the solution, followed by structural weakening of the oxide film due to the formation of Ta(OH) 5 and mechanically fragile Ta-tartarate surface complexes.…”