Self-aligned protective shield for preparing beam-sensitive MEMS-based chip samples using focused ion beam

Focused ion beam (FIB) preparation for transmission electron microscopy (TEM) specimens is widely used across various fields. However, in-situ micro-electro-mechanical systems-based (MEMS-based) chip specimen preparation presents unique challenges, particularly during the transfer stage, which involves transferring and attaching the sample to the MEMS-based chip. Attaching these chips often requires tilting the sample stage, which can cause the ion beam to strike the region of interest (ROI) at a steep, oblique angle. This leads to damage, redeposition, and contamination from ion beam-induced metal deposition. This issue becomes particularly critical for beam-sensitive nanostructures like aligned single-walled carbon nanotube arrays (A-CNTs). To address this, we developed a self-aligned protective shield method. This technique uses the inherent angular offset between the electron and ion beams in a dual-beam FIB system to shield the ROI during critical processing steps. Compatible with standard sampling techniques, our approach effectively mitigates ion beam-induced damage, redeposition and contamination. Controlled experiments on palladium (Pd)–A-CNT–silicon oxide (SiO₂) multilayers, typical contact interface for A-CNT based devices, show enhanced interfacial integrity and structural clarity in scanning TEM (STEM) imaging. Ultimately, our method provides a robust and versatile solution for preparing high-quality cross-sectional TEM lamellae for in-situ MEMS-based chips, offering broad applicability to ion beam-sensitive materials.