Energy Dispersive X-Ray Spectroscopy (Eds/EDX)
Energy Dispersive X-ray Spectroscopy (EDS/EDX) is an analytical technique that identifies the elemental composition of materials by detecting characteristic X-rays emitted when a specimen is bombarded with an electron beam — integrated into SEMs and TEMs as the most accessible and widely used chemical analysis tool in semiconductor failure analysis and process development.
What Is EDS?
- Definition: When a high-energy electron beam strikes a sample, it ejects inner-shell electrons from atoms. As outer-shell electrons fill the vacancy, characteristic X-rays are emitted with energies unique to each element. An energy-dispersive detector measures these X-ray energies and intensities to identify and quantify the elements present.
- Range: Detects elements from beryllium (Z=4) to uranium (Z=92) — covering all elements relevant to semiconductor manufacturing.
- Detection Limit: Typically 0.1-1 atomic percent — sufficient for major and minor constituent identification but not trace analysis.
Why EDS Matters
- Contamination Identification: When a defect or contamination is found on a wafer, EDS immediately identifies which elements are present — pointing to the contamination source.
- Interface Analysis: Composition profiling across interfaces (metal/dielectric, gate stack, barrier layers) reveals interdiffusion, reaction products, and composition gradients.
- Process Verification: Confirms correct material deposition — verifies that the intended elements are present in the right proportions.
- Failure Analysis: Identifies anomalous materials at failure sites — corrosion products, void fillers, foreign materials, and contamination.
EDS Capabilities
- Point Analysis: Focus beam on a specific location — identify all elements present.
- Line Scan: Sweep beam across a line — generate composition profiles showing how elements vary with position.
- Element Mapping: Raster beam across an area — create color-coded maps showing spatial distribution of each element.
- Quantitative Analysis: Calculate atomic and weight percentages of each element using ZAF or Phi-Rho-Z corrections.
EDS Specifications
| Parameter | Modern Silicon Drift Detector (SDD) |
|---|---|
| Energy resolution | 125-130 eV at Mn Kα |
| Detection elements | Be (Z=4) to U (Z=92) |
| Detection limit | 0.1-1 at% |
| Spatial resolution | 0.5-2 µm (SEM), 0.1-1 nm (STEM) |
| Analysis speed | 1-60 seconds per spectrum |
| Mapping speed | Minutes to hours per map |
EDS vs. Other Analytical Techniques
| Technique | Strengths over EDS | When to Use Instead |
|---|---|---|
| WDS (Wavelength Dispersive) | Better resolution, lower detection limit | Overlapping peaks, trace analysis |
| EELS | Better light element, bonding info | TEM thin foil analysis |
| XPS | Surface-sensitive, chemical state | Surface chemistry, oxidation state |
| SIMS | ppb detection limit | Trace contamination, dopant profiling |
EDS is the first-line chemical analysis tool in semiconductor failure analysis — providing rapid, non-destructive elemental identification that guides every investigation from contamination source identification to interface characterization and process verification.