WHAT IT IS
Focused Ion Beam (FIB) is an advanced technique used in electron microscopy systems to precisely mill, cut, image, or modify materials at the micro- to nanometer scale. FIB systems operate by directing a finely focused ion beam (usually gallium ions) onto the sample surface. This enables both material removal (sputtering) and ion-induced deposition, making FIB a powerful tool for sample preparation, nanofabrication, and 3D characterization.
FIB is widely used in semiconductors, materials science, life sciences, and failure analysis, and is often integrated with scanning electron microscopy (SEM) in dual-beam systems.
HOW IT WORKS
A liquid metal ion source (LMIS) – commonly gallium – is heated and ionized.
The resulting positively charged ions are focused into a narrow, high-energy beam using electromagnetic lenses.
When the ion beam hits the sample surface, it causes sputtering, implantation, or chemical changes, depending on the operating mode.
The beam can also induce localized deposition of materials from precursor gases for patterning or protection.
In dual-beam systems, the FIB column is mounted alongside an SEM column, allowing users to image with electrons and simultaneously modify the sample with ions.
TYPES OF FIB MODES AND APPLICATIONSFIB
Milling (Sputtering): Use – Cutting, thinning, or trenching materials. Strengths – Nanometer precision; ideal for preparing TEM lamellae, cross-sections, or microdevices. Limitations – Can cause surface damage or ion implantation; requires careful optimization.
FIB Imaging: Use – High-contrast imaging using secondary ions or electrons emitted during ion beam interaction. Strengths – Reveals compositional and topographical differences; useful for imaging non-conductive materials. Limitations – Lower resolution than SEM; can damage beam-sensitive samples.
FIB-SEM Tomography: Use – 3D reconstruction of materials by sequential slicing and imaging. Strengths – High-resolution 3D maps of complex structures (e.g., pores, interfaces, devices). Limitations – Time-consuming and data-intensive; destructive.
FIB-Prepared TEM Lamellae: Use – Site-specific thinning of samples for TEM or cryo-TEM analysis. Strengths – Enables atomic-resolution imaging of targeted areas (e.g., grain boundaries, defects). Limitations – Sample can be altered by ion beam; requires expertise.
Ion Beam-Induced Deposition (IBID): Use – Creating nanoscale patterns or protective layers (e.g., platinum or carbon). Strengths – Enables nanofabrication, device repair, or site-specific coating. Limitations – Introduces contamination; limited material choice.
IMPACT ON PERFORMANCE
Precision Micro/Nano Engineering: FIB allows for nanometer-scale patterning and manipulation, ideal for device prototyping and structural analysis.
Sample Preparation for TEM and Atom Probe: FIB enables site-specific thinning and cross-sectional cuts, crucial for high-resolution downstream analysis.
3D Characterization: FIB-SEM tomography provides volumetric data with sub-100 nm resolution for materials and biological tissues.
Correlative Microscopy: FIB is frequently integrated with SEM, EDS, EBSD, and cryo-EM platforms, enhancing multimodal analysis.
CHALLENGES AND LIMITATIONS
Ion Damage: Gallium ions can implant into the sample, modify surface chemistry, or cause amorphization.
Cost and Complexity: FIB systems are expensive, require UHV, and need skilled operators for advanced tasks.
Beam-Sensitive Samples: Soft materials, organics, and biological samples may degrade under ion exposure unless cooled (cryo-FIB).
Slow Material Removal: FIB is not ideal for large-volume material removal compared to mechanical or plasma-based methods.
Contamination: Residues from gas injection systems (GIS) and ion beam interaction may contaminate or obscure fine structures.