Resistivity contrast imaging in semiconductor structures using ultra-low energy scanning electron microscopy.

Area of Science:

• Materials Science
• Surface Science
• Electron Microscopy

Background:

• The damage-induced voltage alteration (DIVA) contrast mechanism in Scanning Electron Microscopy (SEM) is crucial for analyzing material properties.
• Understanding contrast mechanisms at ultra-low primary electron beam energies is essential for high-resolution imaging and defect analysis.

Purpose of the Study:

• To investigate the DIVA contrast mechanism in In(0.55)Al(0.45)P irradiated with He2+ ions across a wide range of primary electron beam energies, from 10 keV down to 10 eV.
• To address the challenge of specimen charging in the ultra-low energy range and its impact on SEM contrast for the first time.
• To present experimental data on the influence of beam energy on surface potential formation in insulating materials under electron irradiation in the ultra-low energy regime.

Main Methods:

• Utilized Scanning Electron Microscopy (SEM) to analyze contrast changes.
• Irradiated In(0.55)Al(0.45)P samples with 600 keV He2+ ions.
• Performed imaging and analysis across primary electron beam energies ranging from 10 keV down to 10 eV.

Main Results:

• Observed a dramatic increase in registered signal intensity for primary electron energies below a specific threshold (E1) in the highly resistive irradiated areas.
• This signal increase, contrary to classical total emission yield predictions, is attributed to surface potentials acting as a repeller for primary electrons, leading to signal saturation.
• Provided the first experimental data on beam energy's influence on surface potential formation in insulating materials under electron irradiation within the ultra-low energy range.

Conclusions:

• The study demonstrates that surface potentials significantly influence SEM contrast at ultra-low energies, leading to unexpected signal enhancements.
• Classical models based on total emission yield are insufficient to explain contrast phenomena in the ultra-low energy regime for resistive materials.
• The findings provide novel insights into electron-specimen interactions and charging effects in SEM, particularly for insulating and irradiated materials.