Scanning Electron Microscopy (SEM)
Scanning Electron Microscopy (SEM) encompasses a broad range of techniques which use an electron beam to generate images of a material surface. SEM is used both in independent material characterization and in preparation of samples for analysis via other techniques.
Covalent provides a wide array of capabilities in SEM applications. For a surface-level summary of our SEM services, please refer to the table below, and feel free to contact us with any questions.
|SEM Technique||Typical Applications|
|SEM Imaging ServicesSEM|
CD-SEM (Critical Dimension-SEM)
Large Area SEM
|Imaging of sample surfaces with resolution of ~10nm (SEM) to <1nm (HR-SEM)|
Measurements of surface and topographical features
Bulk processing of particulate samples
Ascertain particle size, feature dimensions, surface characteristics, structures
Includes top-down and cross-sectional variants
Defect characterization: measurements at specific sites of defect size, layer thickness, surface roughness, etc.
Characterization of materials in near-environmental conditions (e.g. at non-ambient temperatures, and/or UHV-atmospheric pressure conditions).
Large area SEM accommodates wafers up to 305 mm diameter!
Assay of variance in manufactured microcrystals.
Image of the pepper-pot nanostructures in butterfly scales which produce structural coloration in the wings
|FIB-SEM (Focused Ion Beam-SEM)||All the imaging capabilities of the HR/SEM techniques maintained|
System includes additional focused-ion-beam column and nanoprobe tool which enables:
Bulk material evacuation / milling; and
Sample manipulation at site-specific locations
Used to prepare electron-transparent cross-sections for TEM analysis.
Image of a TEM lamella prepared from sample cross-section extracted using the nanoprobe tool on a Helios FIB-SEM.
The focused ion and electron beams can also be used to carve functional patterns into semi-conductive or conductive materials via lithography.
|pFIB-SEM (Plasma Focused Ion Beam-SEM)||Delivers the full faculties of the FIB-SEM with improved efficiency and resolution, as well as greater customization in beam chemistries|
System can prepare samples which could not previously have been treated with the Ga ion beam in standard FIB-SEM instruments
Enables milling and cross-sectioning of larger areas of interest (up to 1mm x 1mm x 1mm) in record low times
Peeling revealed in gold film deposited over nanodevice.
|SEM-EDS (SEM-Electron Dispersive Spectroscopy)||All the imaging capabilities of the HR/SEM techniques maintained|
System includes additional x-ray detector(s) which enable:
Chemical composition measurements; and
Compositional mapping of elemental distribution in materials
On top: EDS spectrum generated from a layered region of interest; in middle: map portraying the distribution of several elements of interest selected from the spectrum shown; on bottom: map of oxygen distribution alone: clarifying presence of oxide layers of different degrees of oxygenation.
Scanning Electron Microscopy (SEM & FE-SEM)
Scanning electron microscopy (SEM) is an essential tool for virtually all materials sciences projects, including advanced materials and thin films. SEM measurement techniques are used for high magnification and high-resolution observation of sample surfaces. Scanning electron microscopy uses an electron beam to explore the surface of a sample. The interaction of these electrons with the specimen causes various signals to be emitted, such as secondary electrons, backscattered electrons, Auger electrons, cathodoluminescence, and X-rays. Capturing and analyzing these signals yields a wealth of information about the sample’s morphology and texture, chemical composition, and crystalline structure.
All materials development, thin films development, semiconductors, optical components, and coatings are common uses of scanning electron microscopy.
- Surface imaging
- Particle sizes and features dimensions (including film thickness, features height) with calibrated instruments
- Top-Down SEM: used to image the top surface of the sample to look for defects
- Cross-sectional SEM (X-SEM): used to look at the sample structure
- CD-SEM: used to produce dimensional information such as defect size, layer thickness, surface roughness
- Defect Review SEM: used to navigate to a particular location on a sample normally supplied by another inspection tool and image the defect or help in particle identification
Uses & Limitations:
- What Covalent Metrology’s scanning electron microscopy services are great for:
- Combining surface topography and elemental mapping
- Rapid-high resolution imaging technique
- Sample preparation can be required and destructive (limits on sample size, non-conductive samples need to be coated)
- Functional properties mapping limited
- Surface topography quantification impossible in 3 dimensions
- Samples must be vacuum compatible
- Electrostatically focused SEM required for magnetic samples since magnetic sample’s resolution degraded when magnetically focused systems (the most common type of SEM) are used
Contact us for more information regarding our SEM measurement and imaging services.
Focused Ion Beam SEM (FIB-SEM)
A FIB/SEM tool combines a FIB (focused ion beam) column along with the capabilities of an SEM. The FIB column is typically used for ion-milling of materials (i.e. removal), to enable site-specific investigation of sub-surface features by SEM (i.e. X-SEM). The FIB column can also be used for imaging samples, when electron beam contrast mechanisms fail to produce adequate signal for imaging.
A typical use for FIB-SEM is site-specific TEM sample preparation. Material around a region of interest is milled/removed, and then the sample (lamella, or region of interest) is removed using a nano-manipulated probe and placed on a TEM grid. The lamella is further thinned by the FIB to a final thickness between 20-70nm thick. The FIB also allows users to site specifically deposit Pt or C bands (in situ deposition), which help hold structures together during manipulation. In situ deposition is also particularly important for device editing, generation of ohmic contacts, protecting bean sensitive areas, and other sample-modification applications.
|Top-Down SEM||Uses the electron beam to image the top surface of the sample to look for defects|
|Cross-sectional SEM (X-SEM)||Uses the electron beam to look at the sample structure, layer thickness, layer roughness, voids….|
|Top-down FIB||Uses the ion beam to image the top surface of the sample to look for defects and structure|
|Cross-section FIB||Uses the ion beam to look at the sample structure, layer thickness, layer roughness, voids….|