Improved Electrical Properties and Thermal Stability of GeON Gate Dielectrics formed by Plasma Nitridation of Ultrathin Oxides on Ge(100)

摘要

We demonstrated the impact of plasma nitridation on thermally grown GeO_2 for the purposes of obtaining high-quality germanium oxynitride (GeON) gate dielectrics. Physical characterizations revealed the formation of a nitrogen-rich surface layer on the ultrathin oxide, while keeping an abrupt GeO_2/Ge interface without a transition layer. The thermal stability of the GeON layer was significantly improved over that of the pure oxide. We also found that although the GeO_2 layer is vulnerable to air exposure, a nitrogen-rich layer suppresses electrical degradation and provides excellent insulating properties. Consequently, we were able to obtain Ge-MOS capacitors with GeON dielectrics of an equivalent oxide thickness (EOT) as small as 1.7 nm. Minimum interface state density (D;t) values of GeON/Ge structures, i.e., as low as 3 x 10u cm" eV"1, were successfully obtained for both the lower and upper halves of the bandgap.