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

• Published in: Journal of applied physics 2011-09, Vol.110 (6), p.064103-064103-5
• Main Authors: Hayakawa, Ryoma, Yoshida, Masashi, Ide, Kouta, Yamashita, Yoshiyuki, Yoshikawa, Hideki, Kobayashi, Keisuke, Kunugi, Shunsuke, Uehara, Tsuyoshi, Fujimura, Norifumi
• Format: Article
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3638133

Pure germanium nitride (Ge 3 N 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 3 N 4 thin films formed by AP plasma had superior oxidative resistance compared to those made using conventional plasma techniques. Films fabricated at 500°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 3 N 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 3 N 4 thin films, resulting in superior leakage current. These results suggest that our nitridation technique would show major benefits in Ge field-effect transistors.