Importance of Ge surface oxidation with high oxidation rate in obtaining low interface state density at oxide/Ge interfaces

Abstract

The formation of a gate-insulator/Ge interface with a low interface state density (Dit) starts with oxidation at the Ge surface under appropriate conditions. In this study, a key physical parameter for realizing Dit lower than 1011 eV−1 cm−2 during the oxidation process was clarified by comparison between the experimental results and results calculated based on a proposed model including a time-dependent defect distribution near the Ge-oxide/Ge interface and movement of the interface due to the oxidation at the Ge surface. Dit near the midgap is determined by the competition between the rate of defect creation near the Ge-oxide/Ge interface and the movement rate of the interface, which is the Ge oxidation rate. Oxidation with a Ge oxidation rate of more than 0.1 nm/s can lead to Dit lower than 1011 eV−1 cm−2, taking into account the defect creation rate in a typical Ge device fabrication process, which is 10−2 to 10−4 nm/s.