Demonstration of Monolayer Doping of Five-Stacked Ge Nanosheet Field-Effect Transistors

Abstract

Monolayer doping (MLD) allows devices with complex-geometry structures like nanopillar arrays, nanofins, and nanosheets to be created. These are some of the devices that might be used in next-generation semiconductor technology. Horizontally stacked nanosheet gate-all-around field-effect transistors (GAA FETs), same as gate-all-around nanowire FETs (GAA NW-FETs) technology, have the capacity to extend the technology node down to 5 nm with a good short channel control, which is the current constraint of the existing FinFET. Low-dimensional Ge structures have also attracted a lot of interest with their superior electrical properties compared to standard Si devices. As a result, a fabrication scheme combining high-quality Ge/Si multilayer epitaxy, excellent selective etching control, crystallization by forming gas annealing, and conformal monolayer doping has been demonstrated, allowing for the formation of multilayer stacking of Ge nanosheet gate-all-around field-effect transistors (p-GAA FETs). The crystalline Ge nanosheet is characterized by transmission electron microscopy, and excellent electronic properties are demonstrated using boron-containing molecules for conformal doping to overcome the geometry limitation with two different gate length channels. These successful representations of GAA devices achieved by conformal monolayer doping methodologies can provide significant information for developing emerging three-dimensional (3D) integrated Ge nanodevices beyond a 5 nm generation node.