Structural analysis and electrical properties of pure Ge{sub 3}N{sub 4} dielectric layers formed by an atmospheric-pressure nitrogen plasma

Pure germanium nitride (Ge{sub 3}N{sub 4}) thin films were successfully formed on n-type Ge (111) substrate using an atmospheric-pressure (AP) nitrogen plasma. Their film structures and electrical properties were then examined in detail. Synchrotron radiation photoelectron spectroscopy clearly revealed that the Ge{sub 3}N{sub 4} thin films formed by AP plasma had superior oxidative resistance compared to those made using conventional plasma techniques. Films fabricated at 500 deg. C showed only minor post-oxidation, even after exposure to air, which is a potentially very useful feature for passivation layers at high-permittivity (high-k) dielectric film-Ge interfaces. The films also showed excellent electrical properties. Capacitance-voltage measurements revealed no hysteresis or kinks, indicating that the trap-state density was low at the Ge{sub 3}N{sub 4}-Ge interface. The leakage current density is also lower than in films fabricated using other plasma systems. Direct-tunneling current simulations revealed that the effective tunneling mass increased due to the formation of high-quality Ge{sub 3}N{sub 4} thin films, resulting in superior leakage current. These results suggest that our nitridation technique would show major benefits in Ge field-effect transistors.