# Remote Plasma Selective Silicon Etching Enabled Tunable Sub-Fin Process for Improved Parasitic Bottom Channel Control in Gate-All-Around Nanosheet Field-Effect Transistors

## TL;DR

A new etching technique improves performance of nanosheet transistors by controlling a problematic sub-fin structure.

## Contribution

A remote plasma etching method is introduced to modulate sub-fin profiles in GAA FETs.

## Key findings

- Sub-Fin profiles can be modulated from arrow-shaped to bell-shaped using process parameter control.
- The technique improves thermal resistance and reduces parasitic degradation in nanosheet FETs.

## Abstract

The parasitic Sub-Fin, beneath the stacked nanosheet FETs, limits both leakage and heat dissipation, acting as the bottleneck for improving the performance of NS-FETs. A Sub-Fin edit technology based on remote plasma etching is proposed to modulate the formation of the Sub-Fin. By controlling the process parameters, the Sub-Fin profile can be continuously modulated from “arrow-shaped” to “bell-shaped,” which provides the flexibility to improve the thermal resistance and reduce the parasitic Sub-Fin-induced degradation, making it suitable for low-power and high-performance applications, respectively. The Sub-Fin edit technology is fully compatible with mature Gate-All-Around (GAA) fabrication processes and offers a feasible approach to balancing the trade-off between Sub-Fin degradation and heat dissipation through the Sub-Fin.