Stacked SiGe nanosheets p-FET for Sub-3 nm logic applications

Abstract

The fabrication of vertically stacked SiGe nanosheet (NS) field-effect transistors (FETs) was demonstrated in this study. The key process technologies involved in this device fabrication are low pressure chemical vapor deposition SiGe/Si multilayer epitaxy, selective etching of Si layers over SiGe layers using tetramethyl-ammonium-hydroxide wet solution, and atomic layer deposition of Y₂O₃ gate dielectric. For the fabricated stacked SiGe NS p-GAAFETs with a gate length of 90 nm, I_ON/I_OFF ratio of around 5.0 × 10⁵ and subthreshold swing of 75 mV/dec were confirmed via electrical measurements. Moreover, owing to its high quality of Y₂O₃ gate dielectric, the device showed a very small drain-induced barrier-lowering phenomenon. These designs can improve the gate controllability of channel and device characteristics.