Formation of Ge oxide film by neutral beam postoxidation using Al metal film

A low-temperature neutral beam postoxidation process using an aluminum (Al) metal film was used to obtain a high-quality germanium (Ge) oxide film. After the deposition of a 1-nm-thick Al film on a Ge substrate, the simultaneous oxidation of Al and Ge was carried out at 300 °C, and a Ge oxide film with 28.5% Ge dioxide (GeO₂) content was realized by controlling the acceleration bias power of the neutral oxygen beam. We also confirmed that the fabricated Au/AlOx/GeOx/Ge/Al MOS gate structure shows an equivalent oxide thickness (EOT) of 2.8 nm. This result demonstrates the great potential of neutral beam postoxidation for fabricating high-performance Ge MOS transistors.