3D characterisation using plasma FIB-SEM: A large-area tomography technique for complex surfaces like black silicon

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Black silicon (BSi) exhibits unique properties due to its nanostructured surface.
• Accurate characterization of BSi surface morphology is essential for optimizing its performance in various applications.
• Existing surface topography techniques may fail to detect critical features like under-etched overhangs.

Purpose of the Study:

• To develop and demonstrate an improved method for accurate surface morphology extraction of black silicon (BSi).
• To minimize artifacts and enhance the precision of 3D surface reconstruction.
• To identify and quantify previously undetected surface features like overhangs.

Main Methods:

• Utilized an automated Xe+ plasma focused ion beam (PFIB) and scanning electron microscope (SEM) tomography technique.
• Implemented a novel sample preparation method to reduce ion beam-induced artifacts.
• Applied an optimized post-image processing procedure for accurate 3D model reconstruction.

Main Results:

• Successfully extracted the surface topography of BSi with 2 µm tall needles formed by reactive ion etching (RIE).
• Quantified critical roughness characteristics, including height distribution, correlation length, and surface enhancement ratio.
• Identified under-etched regions with overhanging structures, missed by conventional methods.

Conclusions:

• The presented automated PFIB-SEM tomography method offers high accuracy for BSi surface morphology analysis.
• The detection of overhanging structures is critical for accurate assessment of surface area, reactivity, and light-trapping efficiency.
• This technique is applicable to various BSi surfaces, including those formed by RIE and metal catalyst chemical etching (MCCE).