Study on ultra-thin gate dielectrics: surface preparation and reliability

Wafer preparation and breakdown characteristics are some of the major issues of gate dielectrics in the deep sub-micron regime. In this paper, conventional and a modified HF-last cleaning methods were performed and compared. Dry oxide, N₂O oxynitride and oxide grown on N implanted substrate were used to prepare several kinds of gate dielectrics. The results indicate that after trace amount of IPA was added to HF solution in HF-last cleaning, gate dielectrics showed superior electrical properties. The N₂O oxynitride sample had higher Q_bd than the O₂ oxide sample. In addition, the reversed relation between gate oxide thickness and N implantation dose was observed. Poor breakdown characteristics of gate oxide grown on N implanted substrate was obtained