Comprehensive study of interface passivation in Ge-MOSFETs — Control the interfacial layer for high performance devices

Ge is a promising candidate to replace Si for advanced MOSFET because of its high mobility. Main obstacles to obtain a high-quality high-k/Ge interface for high performance Ge-MOSFETs are: i) thermal instability at the high-k/Ge interface; ii) high-k/Ge interface is highly defective; iii) leakage current through the high-k/Ge stack is high. Therefore, high-k/Ge interface needs to be passivated. In this contribution, various passivation ways including N*-, HCl-, (NH₄)₂S- treatment, and epitaxial BeO layer insertion were investigated. The impacts of these passivation ways in stability enhancement, defects reduction, and gate leakage suppression were discussed.