SEM-EDX：Energy Dispersive X-ray Spectroscopy
Features
EDX, also called EDS, is a technique for elemental and composition analysis based on the energy spectra of the characteristic X-rays generated by electron beam irradiation.
EDX is an optional instrument that often is attached to scanning electron microscopes (SEM) or transmission electron microscopes (TEM). Features include:
- Energy range corresponding to elements B to U
- Energy spectrum can simultaneously be measured in a short time.
- High sensitivity enables low probe currents
- No sample pre-treatment (except for non-conducting samples)
- No prior knowledge of the sample is required.
- Cryogenic sample holder enables measurement of frozen or cooled samples
Application Examples
- Composition analysis of foreign substances
- Visualization of elemental surface distribution
- Visualization of elemental migration by 2D mapping analysis of e.g., conductors in semiconductor devices
- Qualitative and relative semi-quantitative analysis
- Identification of layer structure
- Identification of reactive layers in film interfaces and composition of residues from fabrication/processing
Principle
EDX detects and analyses the energy of the characteristic X-rays that are generated by electron beam irradiation. Since the energy spectrum is unique for each element, the elements constituting the sample can be identified. The intensity of the spectrum yields information about the relative composition.
Process of characteristic X-ray generation
When an atom in the ground state is irradiated with an electron beam (see (1) in Fig. 2), the inner shell electrons are excited at a finite probability, resulting in vacancies in an inner shell (2). An atomic inner-shell vacancy state is energetically unstable, so the outer shell electrons transition to the inner shell (3). Upon this transition, characteristic X-rays corresponding to the energy difference between the outer and inner shells are emitted (4). The X-rays have energies that are characteristic for each element, so it is possible determine the elements from the energy spectrum.
Data examples
Data delivery file format
- Portable document format (PDF), joint photographic expert group (JPEG), and Microsoft® Word® (file type and versions depend on the instrument).
Specifications
Items for enquiries
Purpose and content of measurement
Sample information
1. Number of samples, and availability of preliminary samples
2. Layer structure, film thickness
3. Elements of interest, sample size, availability of cutting the sample
4. Handling instructions
Details on delivery
1. Preferred due date for preliminary analysis report
2. Due date for delivery of final report
Any other issues
Caution
- Liquids need to be solidified for analysis (cryogenic sample holder can be used for this purpose).
- Gases cannot be analysed.
- Insulating samples are subject to a conductive treatment in order to prevent static electric charge accumulation.
- Electron beam broadening limits the minimum region of interest (ROI) to about 0.1-1 μm in bulk samples.
- The minimum resolvable spectral energy is about an order of magnitude larger than that of to wavelength dispersive X-ray (WDX) analysis so there are cases where it is difficult to distinguish elements due to overlapping peaks.
［SEM-EDX］エネルギー分散型X線分光法（SEM）の分析事例はこちらからご覧ください。