When an integrated circuit fails, identifying the damaged component is only part of the challenge. Engineers must determine where the failure occurred, what physical or electrical mechanism caused it, and ultimately why it happened. This requires a combination of specialized IC failure analysis techniques. Some techniques detect electrical abnormalities without physically altering the device. Others allow engineers to see inside an IC package, locate microscopic leakage paths, expose buried semiconductor structures or analyze defects at nanometer-scale resolution. There is no single failure-analysis technique that can solve every problem. A successful investigation normally combines several methods, progressing from electrical characterization and non-destructive inspection toward increasingly localized and potentially destructive physical analysis.
This article explains the major semiconductor and IC failure analysis techniques, what each technique is designed to find, and how engineers decide which method to use. For an overview of the complete subject, see Semiconductor Failure Analysis: The Complete Guide to IC Failure Analysis.
IC failure analysis techniques are the electrical, optical, thermal, imaging and materials-analysis methods used to investigate semiconductor devices that fail to meet their expected electrical or functional behavior.
The techniques generally have one or more of four objectives:
Electrical Failure Analysis (EFA) and Physical Failure Analysis (PFA) are often combined. EFA helps characterize and localize the electrical problem, while PFA is used to physically investigate the suspected region. Thermo Fisher describes semiconductor failure-analysis workflows as combining electrical and physical analysis to localize and characterize defects that affect performance, yield and reliability. The best technique therefore depends on what is already known about the failure.
An engineer investigating an IC with excessive current may begin with electrical characterization and thermal or optical fault localization. An engineer investigating delamination inside a package might begin with Scanning Acoustic Microscopy.
A suspicious particle discovered on a die may require SEM combined with EDS elemental analysis. A transistor-level defect in an advanced device may ultimately require nanoprobing, FIB sample preparation and TEM. The key is to avoid using highly destructive or expensive techniques before the failure has been sufficiently localized.
| Failure or Suspected Problem | Commonly Used Techniques |
|---|---|
| Excessive leakage current | Electrical characterization, EMMI, OBIRCH, thermal analysis |
| Electrical short | EFA, thermal localization, EMMI, OBIRCH |
| Open circuit | Electrical testing, fault isolation, SEM, FIB cross-section |
| Parametric shift | Electrical characterization, nanoprobing, PFA |
| Unknown functional failure | EFA → fault isolation → PFA |
| Internal package defect | X-ray, SAM |
| Package delamination | SAM, cross-section analysis |
| Bond-wire problem | X-ray, optical microscopy, SEM |
| Die crack | Optical microscopy, SAM, cross-section analysis |
| Metal or via defect | EFA, FIB, SEM |
| Contamination or foreign material | SEM + EDS/EDX |
| Transistor-level failure | Nanoprobing, FIB, SEM/TEM |
| Nanoscale structural defect | FIB + TEM |
| Suspected overheating | Thermal imaging, lock-in thermography |
| Buried physical defect | FIB cross-section, SEM or TEM |
The exact workflow depends on the device technology, package construction and nature of the failure, and a laboratory may use several complementary techniques before reaching a conclusion.
Electrical Failure Analysis, or EFA, is usually one of the first stages of an IC failure investigation. Its purpose is to understand how the failing device behaves electrically and, where possible, narrow the problem to a particular circuit block, transistor or physical region.
Typical measurements can investigate:
EFA is particularly valuable because advanced ICs may contain millions or billions of devices. Performing destructive analysis before determining where to look can make the investigation inefficient or even destroy important evidence. Electrical analysis can therefore guide the subsequent physical investigation.
Depending on the failure, EFA may include:
Read the dedicated guide:
Electrical Failure Analysis (EFA) of Integrated Circuits
Optical microscopy is one of the simplest and fastest IC failure analysis techniques. Although its resolution is much lower than SEM or TEM, optical inspection remains useful because many failures can produce visible evidence.
Examples include:
Optical microscopy is often used during initial inspection and again after decapsulation. It is relatively inexpensive and usually non-destructive, making it a logical early step before more sophisticated analysis. Its principal limitation is resolution. As semiconductor features have become smaller, many important defects are far below the practical resolution of conventional optical microscopy.
A packaged IC contains structures that cannot be inspected directly from the outside. X-ray inspection allows engineers to examine many of these internal structures without opening the package.
X-ray analysis can be useful for inspecting:
Because the package does not necessarily need to be opened, X-ray inspection is typically considered a non-destructive analysis technique. This makes it particularly valuable early in package-related investigations. For example, if a BGA device fails electrically, X-ray imaging may reveal an obvious solder or package anomaly before destructive cross-sectioning is considered.
Read more:
X-Ray Inspection of Semiconductor Packages
Some package defects are difficult to identify with optical or X-ray imaging because the problem occurs at an interface between materials. Scanning Acoustic Microscopy, commonly abbreviated SAM, uses acoustic energy to investigate internal structures and interfaces.
SAM is particularly useful for detecting:
It is widely applicable to semiconductor packages because differences or discontinuities at material interfaces can produce acoustic responses that reveal hidden defects. SAM can therefore be particularly valuable when investigating moisture-related damage, package delamination or die-attach problems. The technique is generally non-destructive.
Read more:
Scanning Acoustic Microscopy (SAM) for IC Package Analysis
Some semiconductor defects emit extremely small amounts of light when a device is electrically biased. Emission Microscopy, often called EMMI or photon-emission microscopy, detects these emissions and uses them to help localize electrically active defects. Potential applications include locating:
The technique is valuable because the resulting emission can help guide analysts toward a particular region of the IC before physical material removal begins. NIST has developed time-resolved emission microscopy methods for evaluating switching activity in integrated circuits, demonstrating how optical photon emission from active circuitry can provide information about device behavior. EMMI is therefore primarily a fault-localization technique, not normally the final step in determining the root cause.
Once the suspicious location is identified, FIB, SEM, TEM or another physical technique may be used to investigate the structure.
Read more:
Emission Microscopy (EMMI) for IC Failure Analysis
OBIRCH stands for Optical Beam Induced Resistance Change. The technique uses a focused laser to scan an electrically biased device while monitoring changes in its electrical behavior. Localized heating produced by the laser can change resistance. Abnormal responses can reveal the location of resistive defects. OBIRCH can be useful for locating problems such as:
Like EMMI, OBIRCH is primarily valuable because it can help identify where the problem is located. Once the region has been localized, physical analysis can determine what caused it.
Read more:
OBIRCH Analysis for Semiconductor Failure Analysis
Electrical defects often generate heat. A short circuit, leakage path or high-resistance region can produce a thermal signature that helps analysts locate the failing region.
Several thermal fault-localization techniques are available.
Infrared imaging can reveal relatively strong temperature differences across a powered device. It can be useful for identifying:
Lock-in thermography uses synchronized electrical excitation and thermal detection to identify much weaker thermal signals than conventional thermal imaging can typically reveal. This can make it useful for subtle leakage and defect localization. Thermal techniques are attractive because they can often narrow the search area before the sample is physically modified.
Sometimes the package itself prevents access to the semiconductor die. IC decapsulation, also called decapping, removes package material so the die can be directly examined or analyzed. Decapsulation is not usually a fault-localization technique itself. Instead, it is an important sample-preparation step for techniques such as:
Depending on package construction, chemical, mechanical or other specialized methods may be used. The challenge is to expose the die without destroying the evidence being investigated.
Poorly controlled decapsulation can:
This is why non-destructive inspection should often be completed before decapsulation.
Read more:
IC Decapsulation: Methods, Process and Applications
When defects become too small for optical microscopy, Scanning Electron Microscopy (SEM) becomes one of the most important physical failure-analysis tools. SEM uses a focused electron beam to produce high-resolution images of semiconductor surfaces and prepared cross-sections. Applications include analysis of:
SEM is especially powerful because it can be combined with other analytical techniques. For example, SEM imaging can identify a suspicious particle and EDS/EDX can then help determine its elemental composition. JEOL notes that SEM-EDS is a powerful approach in failure analysis because it can provide both microstructural imaging and elemental analysis.
Read more:
SEM Analysis for Semiconductor Failure Analysis
Focused Ion Beam, or FIB, is among the most important tools for advanced semiconductor failure analysis. Instead of using electrons for imaging alone, FIB directs a focused ion beam at the sample.
The beam can remove material from an extremely specific location. This allows analysts to:
JEOL describes FIB milling as particularly important for semiconductor device failure analysis because a selected target region can be precisely thinned while the milling operation is monitored. Modern instruments frequently combine FIB and SEM in one system. The FIB removes material while the SEM provides high-resolution imaging. This FIB-SEM combination allows analysts to repeatedly mill and inspect a structure until the relevant defect is exposed.
AnySilicon already has further information about this technology:
Many semiconductor defects are buried beneath the surface. To understand these failures, analysts create a physical cross-section through the relevant region. Cross-section analysis may reveal:
Cross-sections can be prepared mechanically or using techniques such as FIB depending on the size and precision required. For highly localized semiconductor defects, FIB allows a cross-section to be created at a carefully selected region rather than broadly cutting through the sample. The resulting structure can then be examined using SEM or, after suitable preparation, TEM.
Finding a particle or unusual region in an SEM image raises another question:
What is it made of?
Energy Dispersive X-ray Spectroscopy (EDS or EDX) helps answer that question.
When the electron beam interacts with a sample, characteristic X-rays are generated. Analysis of those X-rays provides information about the elements present in the selected region.
EDS can be useful when investigating:
SEM-EDS is therefore a particularly useful combination: SEM reveals the shape and location of the abnormal feature, while EDS helps determine its elemental composition. JEOL describes SEM-EDS as useful for failure analysis and the observation and characterization of foreign materials.
However, elemental information alone does not necessarily establish the root cause. The analyst still needs to determine how the material arrived there and whether it actually contributed to the failure.
Read more:
EDS/EDX Analysis in Semiconductor Failure Analysis
As semiconductor devices have become smaller, conventional probing techniques have become increasingly difficult to use for individual structures. Nanoprobing places extremely small probes onto semiconductor circuitry, typically inside an SEM. This allows electrical measurements to be performed on individual devices or very small circuit regions.
JEOL describes nanoprobing systems as using microscopic probes that directly contact semiconductor circuitry inside an SEM to evaluate devices, identify failure locations and investigate failure causes. Transistor I-V characteristics can be evaluated by probing individual transistor electrodes. Nanoprobing can therefore help identify:
The technique can bridge the gap between electrical failure localization and physical analysis. If nanoprobing identifies a specific transistor as abnormal, FIB and TEM can subsequently investigate its physical structure.
Read more:
Nanoprobing for Semiconductor Failure Analysis
For some failures, SEM does not provide sufficient resolution. Transmission Electron Microscopy (TEM) allows structures to be examined at much smaller dimensions and can reveal details unavailable to conventional optical or SEM analysis. TEM can be used to investigate:
Preparing the sample is a critical part of TEM analysis. The area of interest must normally be thinned into an extremely small electron-transparent specimen known as a lamella. FIB is widely used for site-specific TEM sample preparation. Thermo Fisher describes FIB-SEM systems as enabling precise preparation of TEM samples for semiconductor defect and failure analysis. The general workflow may therefore look like:
Electrical failure localization
↓
FIB site-specific sample preparation
↓
TEM analysis
For advanced semiconductor devices, this combination can enable analysis of defects at extremely small dimensions.
Read more:
TEM Analysis of Semiconductor Devices
A common mistake is to view Electrical Failure Analysis and Physical Failure Analysis as competing approaches. They are normally complementary. Consider an IC with unexpectedly high leakage current.
The investigation could proceed like this:
Confirm the excessive current and determine the electrical conditions under which it occurs.
Use EMMI, OBIRCH, thermal techniques or another method to identify the suspicious region.
Decapsulate or delayer the device if necessary.
Expose and inspect the localized region.
If required, investigate the defect at higher resolution or determine its material composition.
Combine the electrical and physical evidence with manufacturing, design and application information. This progression prevents the laboratory from searching blindly across the entire device.
Modern failure-analysis workflows increasingly depend on this combination of electrical localization and physical characterization. Thermo Fisher similarly describes advanced semiconductor FA as combining EFA and PFA workflows.
One of the most important distinctions when planning an FA investigation is whether a technique changes the sample.
Examples include:
These are often performed first because the original sample remains available for additional analysis.
Examples can include:
These techniques may provide far more detailed information, but once material is removed it cannot be restored.
For this reason, failure-analysis workflows normally move from least invasive to more invasive techniques whenever practical.
Once electrical analysis has narrowed the failure to a region of interest, the objective changes. The question is no longer simply:
Where is the problem?
It becomes:
What physical defect is present at that location?
This is the role of Physical Failure Analysis.
PFA may use:
Thermo Fisher identifies PFA and EFA as central approaches for resolving electrical and physical semiconductor defects.
Read our dedicated guide:
Physical Failure Analysis (PFA) of Semiconductor Devices
The challenge of selecting the correct failure-analysis technique increases as semiconductor structures become smaller and more three-dimensional.
Examples include:
JEOL notes that nanometer-scale 3D observation is important for development and failure analysis of newer semiconductor devices with three-dimensional structures.
Advanced logic failure analysis can consequently involve combinations of e-beam probing, FIB and TEM workflows to find increasingly subtle electrical and physical defects.
This makes accurate localization before physical analysis increasingly important.
The answer depends primarily on the symptom and how precisely the problem has already been localized. A useful simplified selection process is:
Start with:
Electrical characterization → EMMI / OBIRCH / thermal localization → PFA
Start with:
Visual inspection → X-ray → SAM → cross-section if necessary
Consider:
Optical inspection → SEM → EDS/EDX
Consider:
Fault localization → FIB cross-section → SEM
Consider:
EFA → nanoprobing → FIB → TEM
Consider:
FIB sample preparation → TEM
The actual investigation should be determined by an experienced FA engineer because every destructive step can remove evidence needed later.
Although every investigation is different, an effective workflow often follows this progression:
1. Understand the failure history
↓
2. Reproduce and electrically characterize the failure
↓
3. Perform non-destructive package inspection
↓
4. Electrically localize the failing region
↓
5. Expose the die if required
↓
6. Perform physical failure analysis
↓
7. Characterize materials and structures
↓
8. Identify the failure mechanism
↓
9. Determine the root cause
↓
10. Recommend corrective action
The analytical technique is therefore only one part of a successful failure investigation.
The real objective is not to produce an impressive SEM or TEM image.
The objective is to establish a defensible relationship between:
Failure symptom → failure location → physical defect → failure mechanism → root cause
Read the detailed workflow:
Semiconductor Failure Analysis Process: From Failure to Root Cause
Common IC failure analysis techniques include electrical characterization, optical microscopy, X-ray inspection, Scanning Acoustic Microscopy, emission microscopy, OBIRCH, thermal imaging, SEM, FIB, EDS/EDX, nanoprobing and TEM.
Different techniques answer different questions, so several methods are often combined during one investigation.
Electrical Failure Analysis (EFA) characterizes and localizes an electrical problem.
Physical Failure Analysis (PFA) physically examines the suspected failing region to identify the structural or material defect.
EFA often precedes PFA.
Yes. SEM is widely used to inspect semiconductor surfaces and cross-sections at much higher resolution than optical microscopy. It can reveal interconnect defects, cracks, contamination and other physical abnormalities.
SEM can also be combined with EDS/EDX for elemental analysis.
Focused Ion Beam technology can precisely remove material from a selected region of a semiconductor device.
It is used for site-specific cross-sections, access to buried structures, circuit editing and TEM sample preparation. JEOL describes FIB milling as especially important for semiconductor device failure analysis.
TEM is typically considered when the feature or defect requiring investigation is too small or structurally complex for conventional optical or SEM analysis.
FIB is commonly used to prepare the extremely thin, site-specific samples required for TEM analysis.
SEM combined with EDS/EDX is frequently used when a suspicious particle or material must be imaged and its elemental composition investigated.
No.
Electrical characterization, X-ray, optical inspection and acoustic microscopy can often be performed without destroying the device.
Decapsulation, cross-sectioning, FIB milling and TEM sample preparation are more invasive and can permanently alter the sample.
Selecting the right failure-analysis method depends on the device technology, package, failure symptoms and the level at which the defect must be localized.
A relatively straightforward package problem may require only X-ray or acoustic microscopy, while an advanced transistor-level failure could require EFA, nanoprobing, FIB and TEM.
If you have a failed IC, semiconductor device or package, AnySilicon can help connect you with companies providing the appropriate failure-analysis capabilities.
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