Using High Dielectric Constant HfO₂/ZrO₂ Superlattice Dielectrics to Enhance Ge Stacked Nanosheets Gate-All-Around Transistor Performance

This study investigated different layer thicknesses of HfO2/ZrO2 superlattice (SL HZO) as gate oxides. Metal-insulator-semiconductor (MIS) and metal-insulator-metal (MIM) capacitors were used to determine the optimal layer thickness of SL HZO for the further advancement of MOSFETs. The HfO2/ZrO2 layers are configured with thicknesses of 0.3 nm/0.3 nm, 0.5 nm/0.5 nm, and 1 nm/ 1 nm per layer. Compared to conventional solid-solution HZO thin films, SL HZO exhibits a higher dielectric constant, a lower interface trap density distribution, a smaller effective oxide thickness, and greater breakdown strength in the time-dependent dielectric breakdown test. In addition, the 0.3-nm SL HZO was used as the gate dielectric in Ge-stacked nanosheets gate-all-around field-effect transistors. The proposed device can achieve higher saturation current and improve the subthreshold swing than the device using HZO as the gate oxide.