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 HfO2 (Ge:HfO2) thin film through interface reactions. In the first experiment, three treatments for forming interfacial layer (IL) were discussed through TiN/2-nm-thick Al2O3/2-nm-thick Ge:HfO2/GeO2/Ge metal-ferroelectric-insulator-semiconductor capacitors. The remnant polarization (Pr), leakage current, and interface trap density (Dit) 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 2Pr value as well as lower Dit values. Next, the thicknesses of Al2O3/Ge:HfO2 would be changed to 4/2 nm and 3/3 nm to investigate the ferroelectricity and leakage current. Although the 3-nm-thick Al2O3/3-nm-thick Ge:HfO2 shows a lower 2Pr value, the leakage current is much lower than 2-nm-thick Al2O3/2-nm-thick Ge:HfO2. The self-induced ferroelectric 3-nm-thick Ge:HfO2 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 > 105 and have high potential in low-power IC applications.