Focused Ion Beam (FIB) technology is one of the most versatile tools used in semiconductor failure analysis and microelectronics characterization. A FIB system directs a tightly focused beam of ions onto a sample. By controlling the beam current, energy, position and scanning pattern, engineers can remove material from extremely specific locations, image structures, expose buried defects and prepare samples for other analytical techniques.
In semiconductor failure analysis, FIB is commonly used for:
Traditional FIB systems have primarily used gallium ions, but newer ion-source technologies—including xenon plasma FIB and lighter helium or neon beams—have expanded the range of applications that can be addressed. Different ion species provide different combinations of milling speed, beam size, sputter rate and imaging characteristics. The result is that FIB has evolved from a specialized semiconductor tool into a broad platform for failure analysis, process development, circuit modification and nanoscale sample preparation.
A Focused Ion Beam instrument generates a beam of ions, accelerates them and focuses them onto a very small region of a sample. When energetic ions strike the surface, they interact with atoms in the material.
Depending on the operating conditions, these interactions can be used to:
One of the reasons FIB is so useful for semiconductor failure analysis is its ability to move between large-volume material removal and very localized nanoscale work.
The uploaded failure-analysis reference describes the gallium liquid-metal ion source as particularly versatile because beam energy, spot size and current can be adjusted for tasks ranging from relatively large excavations to site-specific fabrication at very small dimensions.
This flexibility allows a failure-analysis engineer to first remove substantial material to approach a defect and then reduce the beam current for a much finer final polish.
When energetic ions strike a solid surface, momentum is transferred to atoms in the target. Some of those atoms can be ejected from the surface. This process is known as sputtering. By scanning the ion beam repeatedly over a defined pattern, the FIB system can progressively remove material.
This allows the operator to create:
The amount of material removed depends on several factors, including:
Higher currents generally increase material-removal speed but provide less suitable conditions for the final high-quality surface. For this reason, semiconductor FIB work often involves:
High-current bulk milling
↓
Intermediate milling
↓
Low-current final polishing
The lower-current finishing step helps remove material redeposited during aggressive milling and improves visibility of the Region of Interest (ROI).
Different ion sources offer different advantages. The uploaded failure-analysis reference discusses three particularly important classes:
The Gallium Liquid Metal Ion Source (Ga LMIS) has been widely used since the 1980s for semiconductor failure analysis, mask repair and circuit editing. Gallium remains one of the most commonly used FIB ion species because the beam can be operated over a wide current range.
Typical applications include:
The uploaded reference reports Ga FIB operation ranging from sub-picoamp currents to around 100 nA, allowing one instrument to perform both fine and comparatively aggressive milling operations.
Plasma FIB (PFIB) typically uses xenon ions. Xenon’s larger mass and the ability of plasma sources to deliver much higher beam currents make Xe PFIB particularly useful when substantial volumes of material need to be removed. According to the uploaded failure-analysis reference, xenon PFIB can achieve material-removal rates more than twenty times greater than conventional gallium FIB in suitable applications.
This makes Xe plasma FIB useful for:
Xe PFIB systems can operate at currents exceeding 1 µA, compared with roughly 100 nA maximum currents described for Ga FIB in the reference. The trade-off is that a high-current Xe beam is not necessarily the best option for every extremely fine operation. The ion source should therefore be selected according to the scale of the material removal and required precision.
Lighter ion species provide another set of capabilities. The reference describes helium and neon beams based on Gas Field Ion Source technology. Neon offers a relatively small spot size and lower sputter rate than gallium while also producing a strong secondary-electron signal. This combination can be attractive when a process requires:
The reference reports a neon probe size below approximately 2 nm under the cited operating conditions and notes that the strong secondary-electron signal can be useful for determining when milling has reached a desired layer. Helium provides still finer imaging and fabrication capabilities but has a much lower sputter rate, making it less appropriate for large-volume material removal.
| FIB Source | Main Strength | Typical Semiconductor Applications |
|---|---|---|
| Gallium FIB | Broad balance of precision and milling capability | Cross-sectioning, TEM preparation, circuit edit, probe pads, tomography |
| Xenon Plasma FIB | High material-removal rate | Large cross-sections, bulk silicon removal, packages, BEOL analysis, tomography |
| Neon FIB | Fine beam with controlled sputtering | Precision milling, circuit modification, high-aspect-ratio vias |
| Helium Ion Beam | Very small probe and high-resolution imaging | Surface imaging, nanoscale modification and fine deposition |
No single ion source is ideal for every FIB application. Modern failure-analysis workflows may select the source according to the required combination of material-removal rate, resolution and endpoint control.
One of the most important developments in FIB technology is the integration of a Focused Ion Beam with a Scanning Electron Microscope (SEM). This configuration is generally known as FIB-SEM or a dual-beam system.
The principle is straightforward:
The FIB removes material
while
The SEM images the exposed structure.
This makes it possible to repeatedly alternate between milling and imaging without transferring the sample to another instrument.
The uploaded reference notes that combining FIB cross-sectioning with SEM imaging in one instrument has led to widespread use of FIB-SEM systems. A common geometry places the SEM vertically and the FIB column at an angle of approximately 52–55 degrees relative to it.
A typical workflow is:
Locate ROI with SEM
↓
Mill using FIB
↓
Inspect newly exposed surface using SEM
↓
Continue milling
↓
Stop when defect is reached
↓
Perform high-resolution imaging or further analysis
This workflow is extremely useful in semiconductor failure analysis because many defects are buried beneath the surface.
Modern FIB-SEM platforms can contain several detectors and analytical tools. The uploaded reference describes configurations that may include:
Backscatter detectors can also be used to monitor FIB milling because different materials can generate different contrast. Combining these capabilities means that the instrument can do much more than simply cut a sample.
It can potentially:
Mill → image → analyze → continue milling
within the same platform.
Modern FIB instruments may also incorporate a Gas Injection System (GIS). A GIS introduces a precursor gas through a small needle positioned close to the sample. When the precursor interacts with the ion or electron beam, chemical reactions can be used to assist either:
This significantly extends what FIB systems can do. The uploaded reference describes GIS as an important complementary technology for beam-induced deposition and etching.
Beam-induced deposition can be used to create structures such as:
Metal precursors can be used to deposit conductive materials in a defined region. This capability is particularly useful for circuit editing, where FIB may first cut an existing conductor and then deposit a new conductive path.
Chemical assistance can also improve material removal. Different chemistries can enhance etching of selected materials and therefore increase selectivity between layers.
The objective is not simply faster milling. Selective chemistry can make it easier to remove one material while limiting removal of another. This becomes increasingly valuable in semiconductor devices composed of many alternating layers of metals and dielectrics.
Focused Ion Beam technology plays a central role in Physical Failure Analysis (PFA). Electrical failure-analysis methods may first identify a suspicious region. The FIB can then physically expose that location.
For example:
Electrical leakage detected
↓
Fault localization identifies ROI
↓
FIB cross-section exposes buried structure
↓
SEM images the structure
↓
TEM or materials analysis if required
↓
Physical defect identified
The value of FIB is therefore its ability to access an exact site rather than broadly destroying or sectioning the entire device. See also Physical Failure Analysis (PFA) of Semiconductor Devices.
One of the most common semiconductor FIB applications is site-specific cross-sectioning. A defect may be buried inside:
A FIB can remove material directly adjacent to the suspected defect and create a vertical surface that can then be imaged. This is particularly valuable when electrical failure analysis has already identified a very small Region of Interest.
A simplified process is:
The uploaded reference stresses that high-current milling can increase redeposition, so a lower-current final polishing step is required to reveal the actual ROI cleanly.
FIB can also prepare samples for analytical techniques such as:
The book describes creating inclined trenches with FIB to expose deeper structures and effectively enlarge thin layers for subsequent examination. This can improve access to structures that would otherwise be difficult to evaluate using only top-down surface analysis.
One of the most important advanced applications of FIB is the preparation of samples for Transmission Electron Microscopy (TEM). TEM requires an extremely thin specimen. The uploaded reference describes FIB preparation of electron-transparent semiconductor samples with thicknesses below approximately 50 nm, allowing high-resolution TEM examination of precisely selected structures. This is particularly powerful for failure analysis because the TEM specimen can be prepared from an exact known defect location.
Examples include:
A typical workflow is:
Electrical fault localization
↓
SEM/FIB navigation
↓
FIB exposes ROI
↓
Thin lamella is prepared
↓
Lamella is transferred
↓
TEM analysis
The result is site-specific high-resolution analysis rather than random examination of the semiconductor structure.
A TEM lamella is an extremely thin slice of material prepared so that electrons can pass through it during transmission electron microscopy. FIB is particularly effective for producing TEM lamellae because it can target a very small physical location. The FIB first removes surrounding material and leaves a thin section containing the Region of Interest. That section is then progressively polished until it becomes sufficiently thin for TEM imaging. The ability to prepare a TEM sample from one specific transistor or memory cell is one reason FIB has become such an important semiconductor-analysis technology.
One important FIB artifact is redeposition. Atoms removed during sputtering do not necessarily leave the sample completely. Some can redeposit onto nearby surfaces.
This can:
The uploaded failure-analysis reference discusses milling-pattern strategies specifically designed to reduce redeposition and recommends a fine final polishing step after high-current material removal.
Careful choice of beam direction and milling pattern can therefore significantly improve cross-section quality.
Another common artifact is known as curtaining. Curtaining appears as vertical streaks or shadow-like features on a milled surface. It commonly occurs when the ion beam passes through materials with different sputter rates. This is particularly relevant to semiconductors because IC structures contain alternating layers of:
The differences in milling behavior can project patterns through the cross-section. The reference identifies curtaining as a significant problem in semiconductor FIB sample preparation.
Several strategies can reduce curtaining. One relatively straightforward approach is to mill at a slight angle rather than exactly perpendicular to the sample. More advanced approaches change the incident beam angle continuously using rocking stages. The reference describes both off-axis polishing and continuous rocking methods for reducing curtaining in semiconductor structures such as 3D NAND. For some applications, the sample can also be prepared from the opposite direction.
Backside or inverted milling can be particularly valuable when the important Region of Interest is located near the transistor level. In a conventional top-down structure, the beam may first encounter many metal layers and contacts before reaching the transistors. Those structures can produce significant curtaining. With backside preparation, the sample is oriented so that the beam approaches through relatively uniform silicon before reaching the active structures. The uploaded reference notes that this can substantially reduce curtaining from metal lines when the real analytical target is the transistor rather than the overlying interconnect. The trade-off is that backside TEM preparation is typically more time-consuming and requires suitable instrument and sample-handling capability.
FIB preparation itself can modify the sample. This is one of the most important considerations in high-resolution failure analysis. Ion bombardment can create:
The reference identifies ion-beam-induced damage as a fundamental challenge in FIB sample preparation, particularly where subsequent analysis requires extremely accurate structural information.
The risk can be reduced by:
The preparation method must therefore be selected according to what the subsequent analytical technique needs to measure.
FIB can also prepare specimens for Atom Probe Tomography (APT). APT requires a very different sample geometry from TEM. Instead of a thin lamella, the specimen must generally be shaped into a very sharp needle or tip.
FIB-SEM can be used to extract a site-specific Region of Interest and progressively shape it into the required geometry. The reference notes that APT preparation shares some of the same concerns as TEM preparation—including curtaining and beam-induced damage—but also requires extremely accurate control of the tip shape and geometry.
FIB-SEM can also be used to reconstruct semiconductor structures in three dimensions. A typical FIB tomography workflow repeatedly performs:
Mill a thin slice
↓
SEM image the exposed face
↓
Mill another slice
↓
Acquire another image
This operation may be repeated hundreds or thousands of times. The images are then aligned and reconstructed into a three-dimensional representation of the structure. The uploaded reference describes 3D FIB data collection involving hundreds to thousands of images and notes that automation is essential for practical acquisition and analysis.
Applications can include analysis of:
Historically, advanced FIB work required significant manual operator skill. Modern systems increasingly use software automation. The uploaded reference describes recipe-based automated FIB workflows that can execute predefined milling and preparation sequences.
Automation can include:
Fiducial markers can be monitored automatically to compensate for drift during long milling sequences. The reference describes automated routines capable of preparing arrays of TEM lamellae with minimal operator intervention.
This is particularly valuable in semiconductor manufacturing and process development where multiple sites need to be analyzed consistently.
Automation becomes even more important for tomography. During long serial-sectioning runs, the system may automatically adjust:
The reference reports automated processes capable of maintaining approximately 3–5 nm slice thicknesses during extended FIB tomography runs under the described conditions. The resulting data can then be analyzed using software to measure attributes such as:
Such workflows are increasingly relevant as semiconductor architectures become more three-dimensional.
Circuit edit remains an important application of FIB, but it is only one part of the technology.
FIB circuit edit allows engineers to:
The uploaded reference describes circuit edit as a way to physically simulate a design change on existing silicon before committing to a mask change. Because AnySilicon has a separate detailed article dedicated to this application, readers should see FIB Circuit Edit for a deeper explanation of first-silicon debugging, ECO validation and circuit modification.
FIB is becoming more important as semiconductor structures become smaller and more three-dimensional.
Modern devices can include:
These structures create two competing requirements:
More material may need to be removed
while at the same time
the final Region of Interest becomes smaller.
This is one reason different FIB sources have emerged. Xe plasma FIB provides high-volume material removal, while Ga, Ne and other ion beams can provide different levels of precision and milling control. The book emphasizes that improved beam-placement accuracy, patterning control and process monitoring are becoming increasingly important as semiconductor structures continue to scale.
FIB is not limited to the semiconductor die itself. Plasma FIB systems can remove enough material to analyze larger package structures. In the package-failure-analysis section of the uploaded reference, plasma-assisted FIB is described as particularly useful for cross-sectioning structures such as solder bumps because ion milling can avoid some of the smearing and mechanical artifacts introduced by conventional manual cross-sectioning.
Potential applications include:
For especially large structures, PFIB’s greater material-removal capability can make analysis practical where conventional Ga FIB would require significantly longer milling time.
Both methods are useful, but they address different requirements.
Can be attractive for:
Is especially valuable when:
In many investigations, mechanical preparation may bring the sample close to the ROI and FIB may then perform the final high-precision preparation.
The best FIB method depends on the analytical problem.
Consider:
Xe plasma FIB
Consider:
Ga FIB / FIB-SEM
A lighter-ion system such as:
Ne FIB
may offer advantages for suitable applications.
Use:
FIB-SEM → site-specific lamella preparation → TEM
Use:
FIB-SEM serial sectioning → automated 3D reconstruction
Use:
FIB circuit edit
The FIB source and preparation strategy should therefore be selected according to the scale of the target, material system, required precision and analysis that will follow.
| Application | FIB Function | Typical Next Step |
| Buried defect analysis | Site-specific cross-section | SEM imaging |
| Via/contact failure | Expose exact interconnect | SEM or TEM |
| Microbump failure | Cross-section package structure | SEM |
| Nanoscale transistor defect | Prepare thin lamella | TEM |
| Material-analysis preparation | Expose deeper layers | AES/SIMS/material analysis |
| 3D structure analysis | Serial slicing | 3D reconstruction |
| Circuit debug | Cut/deposit/reroute | Electrical testing |
| APT preparation | Shape site-specific tip | Atom Probe Tomography |
The major advantages of FIB include:
The technique is especially powerful when it follows accurate electrical fault localization. Instead of searching randomly for a defect, the analyst can use FIB to expose the exact location identified electrically.
FIB is powerful, but it is not artifact-free. Important considerations include:
At increasingly small dimensions, preparation quality can directly determine whether the physical defect remains visible. For this reason, failure analysts must distinguish between the original semiconductor defect and any feature introduced during FIB preparation.
FIB stands for Focused Ion Beam.
It is a technology that directs a tightly focused ion beam onto a semiconductor sample to image, mill, expose or modify very small structures.
Common applications include:
FIB-SEM combines a Focused Ion Beam with a Scanning Electron Microscope.
The FIB removes material while the SEM images the resulting surface, allowing repeated milling and inspection within the same instrument.
Gallium FIB provides a broad combination of precision and material-removal capability and is widely used for semiconductor cross-sectioning, TEM preparation and circuit edit.
Xenon plasma FIB can deliver much higher currents and substantially faster bulk material removal, making it attractive for large cross-sections, packages and high-volume milling.
TEM requires an extremely thin specimen from the correct Region of Interest.
FIB can target a specific transistor, memory cell or interconnect and produce an electron-transparent lamella for TEM analysis. The uploaded reference describes FIB preparation of semiconductor TEM samples below approximately 50 nm thickness.
Curtaining is a streaking artifact that can appear when different materials mill at different rates.
It is particularly relevant to layered semiconductor devices containing alternating metals and dielectrics. Off-axis polishing and rocking techniques can help reduce the effect.
Yes.
Ion bombardment can introduce implantation, amorphization or other structural damage.
Lower-energy and lower-current final polishing and optimized preparation methods are used to reduce these effects.
Yes.
FIB can cut existing interconnects and, with beam-induced deposition, create new conductive paths or probe structures.
For a detailed explanation, see FIB Circuit Edit.
FIB tomography repeatedly removes thin slices from a sample and records SEM images after each slice.
The resulting image stack is reconstructed into a three-dimensional representation of the structure. Modern workflows can automate hundreds or thousands of milling and imaging cycles.
FIB is most powerful when used as part of a systematic semiconductor failure-analysis process.
A typical investigation may proceed as follows:
Electrical failure detected
↓
Electrical Failure Analysis
↓
Fault localization
↓
Region of Interest identified
↓
FIB exposes the defect
↓
SEM / TEM / materials analysis
↓
Physical defect identified
↓
Failure mechanism established
↓
Root cause determined
FIB therefore provides the critical link between knowing where an electrical problem is located and physically seeing the structure responsible for it.
As semiconductor devices become increasingly complex and three-dimensional, that ability to selectively access specific nanoscale structures will remain an important part of advanced semiconductor failure analysis.
If you need FIB analysis for an IC, semiconductor device, wafer or package, AnySilicon can help connect you with companies and laboratories providing appropriate failure-analysis capabilities.
Typical requirements may include:
When requesting support, provide information about the semiconductor technology, package, suspected failure location, analysis already performed and the type of FIB work required. This can help identify the most appropriate laboratory, ion source and sample-preparation workflow.
