Self-Induced Ge-Doped HfO₂ Applied to Ge Stacked Nanowires Ferroelectric Gate-All-Around Field-Effect Transistor with Steep Subthreshold Slope Under O₃ Treatment with GeO₂ as Interfacial Layer

This study reports a self-induced ferroelectric Ge-doped HfO 2 (Ge:HfO 2 ) thin film through interface reactions. In the first experiment, three treatments for forming interfacial layer (IL) were discussed through TiN/2-nm-thick Al 2 O 3 /2-nm-thick Ge:HfO 2 /GeO 2 /Ge metal-ferroelectric-insulator-semiconductor capacitors. The remnant polarization (P r ), leakage current, and interface trap density (D it ) were compared to select the most appropriate IL treatment. The results show that the in-situ ozone treatment under the standard atomic layer deposition process had the second highest 2P r value as well as lower D it values. Next, the thicknesses of Al 2 O 3 /Ge:HfO 2 would be changed to 4 nm/2 nm and 3 nm/3 nm to investigate the ferroelectricity and leakage current. Although the 3-nm-thick Al 2 O 3 /3-nm-thick Ge:HfO 2 shows a lower 2P r value, the leakage current is much lower than 2-nm-thick Al 2 O 3 /2-nm-thick Ge:HfO 2 . The self-induced ferroelectric 3-nm-thick Ge:HfO 2 thin film was then applied to fabricate Ge stacked nanowires gate-all-around field-effect transistor. The results show a steep subthreshold slope of 58 mV/dec for pFET and on-off current ratio > 10 5 and have high potential in low-power IC applications.