Wet cleaning of cross-contamination of high-k dielectrics in plasma etch tool

Direct tunneling through the gate SiO2 (εr ≈4) has become a serious concern for metal-oxide semiconductor field effect transistor scaling. The semiconductor industry is focusing on dielectrics with high relative dielectric constants (εr 10) to replace SiO2 gate oxides. Among the potential high- k materials, oxides and silicates of hafnium (Hf) have shown the most promise. The possibility of process cross-contamination by integrating these materials into silicon processes is a major concern for integrated circuit manufacturers. Cross-contamination of Hf in a plasma etch tool has been investigated. These studies confirm that significant cross-contamination occurs when HfO2 is etched in a chloro-fluoro-carbon plasma etch system. None of the standard cleaning processes commonly used in the semiconductor industry (such as SC1 and SC2) completely remove the contamination; however, dilute hydrofluoric acid, hydrofluoric acid-hydrogen peroxide water mixture, and SC1 cleans removed contamination below the concentration thresholds for oxide degradation and close to the total reflection X-ray fluorescence detection limit.