# Carrier Mapping in Sub‐2nm Node Nanosheet Transistors with Scanning Spreading Resistance Microscopy

## TL;DR

Researchers improved a microscopy technique to map charge carriers in ultra-thin nanosheet transistors, revealing how heat treatment affects material properties.

## Contribution

The first carrier mapping in 5.5 nm thick nanosheet channels using optimized SSRM is demonstrated.

## Key findings

- SSRM was optimized to map carriers in 5.5 nm thick nanosheet channels.
- Rapid thermal annealing increased phosphorus diffusion by ∼5 nm.
- SSRM results matched semi-atomistic simulations of junction formation.

## Abstract

As the semiconductor industry transitions to gate‐all‐around architectures such as Nanosheet‐FETs (NSFETs) for the 2nm node and beyond, controlling parasitic resistance through precise junction engineering is fundamental. This requires characterization methods capable of mapping active carriers with nanometer‐scale resolution. This work demonstrates a significant advancement in scanning spreading resistance microscopy (SSRM) that enables, for the first time, carrier mapping within 5.5 nm thick nanosheet channels. This was achieved through a systematic optimization of sample preparation to achieve sub‐nanometer topography, the use of ultra‐sharp diamond probes, and the implementation of a linear current amplifier to eliminate artifacts from slow logarithmic amplifiers. SSRM measurements of NSFETs with and without a 950°C rapid thermal anneal reveal a clear increase in phosphorus diffusion due to the higher thermal budget, with carrier profiles in excellent agreement with Kinetic Monte Carlo process simulations. This demonstrates how SSRM is a valuable characterization technique for providing direct feedback on junction formation in advanced gate‐all‐around devices.

Within this work, advancements in scanning spreading resistance microscopy (SSRM) allow charge carrier mapping within 5.5 nm‐thick nanosheet channels. Devices subjected to rapid thermal annealing at 950°C show ∼ 5 nm enhanced phosphorus diffusion, with profiles in close agreement with semi‐atomistic process simulations. This establishes SSRM as a unique technique that provides direct insight into junction formation in advanced gate‐all‐around architectures.