Time dependent changes in Schottky barrier mapping of the W/Si(001) interface utilizing Ballistic Electron Emission Microscopy

TL;DR

This study uses Ballistic Electron Emission Microscopy to monitor nanoscale changes in the W/Si(001) Schottky barrier over 21 days, revealing interface evolution and silicide formation without significant I-V variation.

Contribution

It demonstrates the capability of BEEM to detect nanoscale interface changes and correlates these with silicide formation over time.

Findings

Schottky barrier height decreases from 0.71 eV to 0.62 eV over 21 days

Spatial uniformity of the barrier map decreases significantly

Silicide formation increases at the interface over time

Abstract

The W/Si(001) Schottky barrier height is mapped to nanoscale dimensions using BEEM over a period of 21 days to observe changes in the interface electrostatics. Initially the average spectrum is fit to a Schottky barrier height of 0.71 eV and the map is uniform with 98% of the spectra able to be fit. After 21 days, the average spectrum is fit to a Schottky barrier height of 0.62 eV and the spatial map changes dramatically with only 27% of the spectra able to be fit. Transmission electron microscopy shows the formation of an ultra-thin tungsten silicide at the interface which increases in thickness over the 21 days. This increase is attributed to an increase in electron scattering and the changes are observed in the BEEM measurements. Interestingly, little to no change is observed in the I-V measurements throughout the 21 day period.