Characterization of Chemical Bonding Features and Interfacial Reactions in Ge-MIS Structure with HfO2/TaGexOy Dielectric Stack

Abstract

As means to control interface reactions between HfO2 and Ge(100), chemical vapor deposition (CVD) of ultrathin Ta-rich oxide using tris(tert-butoxy)(tert-butylimido)tantalum (Ta-TTT) on chemically-cleaned Ge(100) has been conducted prior to atomic-layer controlled CVD of HfO2 using tetrakis (ethylmethylamino) hafnium (TEMA-Hf) and O3. An impact of post metallization annealing (PMA) in N2 ambience on chemical structure and electrical properties for TiN-gate Ge-MIS structure has been investigated. Hard x-ray photo-emission spectroscopy (HAXPES) measurements under synchrotron radiation with the excitation energy of 7939 eV show that good thermal stability of MIS structure against PMA at temperature of 400 °C. Diffusion of Ge atoms into stack dielectrics and TiN was observed after PMA at temperatures over 500 °C. As for the electrical properties of MIS capacitors, PMA at 300 °C was found to be effective to reduce the hysteresis due to charge trap and gate leakage current through the dielectrics. It was also found that the relative dielectric constant of interfacial TaGexOy thin layer was ~ 9, and calculated equivalent SiO2 thickness (CET) of 1.0 nm can be achieved for the sample with 3 nm thick HfO2/1nm-thick TaGexOy stack dielectrics.