Germanium p MOSFET with HfON gate dielectric

Germanium is promising for future advanced CMOS devices because of its high mobility. But the lack of a stable Ge oxide makes it difficult to fabricate a germanium MOSFET. Inspired by the recent progress of high-k dielectric gate stack in Si MOSFET applications, the MOSFETs with Ge substrate have attracted more and more attention again. High-mobility p-channel germanium MOSFETs with ultra low EOT (6-10Å) have been reported with ultra-thin ZrOz.' Among various high-K gate dielectrics, HtO2 and Hf based dielectric materials have been researched as the most promising candidates for gate stack. Bai et al studied the Ge MOS capacitors with HfO₂ dielecmcs.' It was found that the HfO₂ without surface nitridation showed both a large EOT and a large leakage current density, while surface nitridation can suppress the interfacial growth and further achieve a small EOT and low leakage current at the same time. However, surface nitridation increases the process complexity and the presence of hydrogen increases the trapping rates. Hahium.oxynitride HfO_x,NHfO_y has been proved to be a high stable gate dielectric material with simple process procedure. It has higher crystallization temperature which may be beneficial to keep a low leakage current, and the nitrogen incorporation strengthens the immunity to oxygen diffusion which can suppress the interfacial layer growth for a low EOT. In this work, we studied the electrical performance of Ge MOSFET with a thin Hf0_x,NHf0_y gate dielectric.