Electrical properties of plasma-grown oxide on MBE-grown SiGe

Abstract

The oxidation of semiconductors by RF (radio-frequency) plasma anodization offers several advantages over conventional thermal furnace oxidation, such as low process temperature and faster oxidation rate. This paper investigates the electrical properties of the plasma-grown oxide on SiGe at room temperature and compares them with thermally grown oxides of SiGe. An interface state peak has been observed at around E_v+0.75 eV. This peak is found to be caused by the presence of the SiGe layer and we present evidence that it is related to a silicon dangling bond. We have also observed that the magnitude of the voltage pulse necessary to induce avalanche electron injection increases through the presence of the SiGe layer. We believe that this is related to the increased ionization rate associated with the smaller bandgap of SiGe. The presence of Ge atoms in the plasma oxide has introduced electron traps with capture cross sections of the order of 10^-15 and 10^-16 cm². Negative bias temperature stress indicates that the bonding between Ge and H is weak. This aging test also supports the theory that the interface states are acceptor-like in the upper half and donor-like in the lower half of the energy bandgap.