Scanning Electron Microscopy (SEM) Analysis and Imaging Services
Scanning electron microscopy (SEM) analysis is an essential tool for many disciplines within the engineering and materials sciences. SEM material analyses are capable of delivering high-magnification and high-resolution images to characterize a diverse range of sample surface types.
Spatial resolution in microscopy is limited by the energy of the probe particle. Thus, using electrons instead of photons enables us to capture images with resolution up to several tens of thousands of times greater than traditional optical microscopes.
To generate these electron images called micrographs of a sample using scanning electron microscopy analysis, a highly focused electron beam spot is scanned over the material’s surface. Electrons within the applied beam will interact with the sample, producing secondary electron emissions, back-scattered electrons, Auger electrons, cathodoluminescence and X-ray signals. Different detectors on an SEM capture these signal particles to produce a wealth of information about the sample’s morphology, texture, chemical composition and crystalline structure.
There are numerous different techniques within SEM imaging.
SEM SURFACE ANALYSIS IMAGING MEASUREMENTS
- SEM Morphology Analysis: detailed characterization of the shape and structural features of a surface’s topography
- Dimensional measurement of micro- and nano-scale structures (e.g. film thickness, feature height)
- Top-Down SEM: imaging from the top of a material to scan for defects
- Cross-sectional SEM: used to evaluate sample structures in cross-section, produced by preliminary mechanical cuts or trenching via Focused Ion Beam-SEM (FIB-SEM; please see our page on FIB-SEM services for more details).
- Environmental SEM: cross sectional or top-down measurements taken at specific pressure / temperature conditions to characterize material morphology
- Critical dimension-SEM: dimensional data on particle or defect size, structure, layer thickness, and surface roughness. Can be performed at specific locations identified by other inspection tools to assay specific defect properties (Defect Review-SEM).
- Large-area SEM: standard imaging services in an XL-tool with a sample chamber big enough to admit wafers up to 300 x 300 mm.
Uses & Limitations of SEM Imaging
- What it’s great for:
- High-resolution imaging of material features on micro-scale
- Morphology characterization of both organic and inorganic materials
- Semiconductor and device refinement / error analysis
- Specimen damage is possible due to exposure to high-energy electron beam with current concentrated at a point
- Size limits apply to specimens; cannot resolve all nanostructures (<1-10nm, depending on tool).
Instruments we use for SEM Imaging
FEI Helios 600i, 650, 660, 660i: This family of high-resolution field-emission SEMs can resolve structures as small as 0.8nm. Field-immersion optics, drift-corrected imaging, and stage biasing features bolster the best-in-class Elstar Schottky electron source for optimized performance. Each system is further equipped with FEI’s top-of-the-line Elstar Ultra-High-Res Through-the-Lens Detector (TLD) – which offers the highest collection efficiency of secondary electrons (SE)and on-axis back-scattered electrons (BSE) – as well as a suite of advanced detectors which confer low-kV SE/BSE detection and high-angle annular dark-field imaging capabilities with maximal signal/noise ratio. Helios SEMs incorporate a high-precision, piezo-driven 5-axis motorized stage to navigate around a total field of view 150mm in diameter with full rotational control.
FEI Quanta 200 ESEM / VPSEM: The Quanta 200 from FEI is used to perform environmental-SEM measurements. Our tool is outfitted with a tri-ocular imaging and visualization system to characterize profile, area, volume, roughness, and waviness of materials. It has a highly sensitive BSE for Z-contrast imaging, and a panchromatic cathodo-luminescence detection system. A specialized backscatter detector enables orientation imaging and texture mapping of crystalline and polycrystalline materials at variable temperature / pressure. In particular, this instrument’s exchangeable hot- and Peltier cold-stage accessories enable wet chemistry (above partial pressure of H2O) and in situ annealing experiments to be performed and recorded at temperatures ranging from below 0 to 1000 C.
Hitachi S-4700: Another field-emission SEM from one of the global leaders and most trusted manufacturers of electron microscopes. This system is particularly well suited to high-magnification imaging with high depth-of-field.
ZEISS Ultra-55: This field-emission SEM is capable of imaging resolutions down to 2nm. The innovative electrostatic final-lens design permits longer working distances and consequently excellent resolution for ferrous and ferromagnetic samples. Beam deflection in this system is exquisitely fine-tuned,facilitating precision electron beam lithography. High-resolution, high-depth-of-field imaging is made possible using an updated ESB detector system with an integrated, specialized filtering grid.
FEI XL835: This is another field-emission type SEM with a specially designed oversize sample chamber, accommodating samples up to 305mm x 305mm. The tool