Scanning Electron Microscopy Inspection
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Images are produced by scanning a
focused
electron beam across the surface of a specimen. In the most common mode, the low energy secondary
electrons emitted
are detected and used to modulate the brightness of a synchronously scanned CRT.
Other signals can also be
detected. X-rays, characteristic of that part of the specimen probed by the electron beam,
allow both a
qualitative and quantitative determination of the elements present in the selected region.
High energy
backscattered electrons can be separated and used for image formation. Since the backscattering
efficiency
is a function of atomic weight, this image reveals compositional variations due to average atomic
number.
Metal Inspection
° MIL-STD 883, Method 2018
° MIL-STD 750, Method 2077
Information
Obtained
° Surface topography if low energy secondary electrons
are collected
° Atomic number or orientation information if higher
energy backscattered
electrons are used for imaging
° Differentiation between surface roughness, porosity,
granular deposits,
stress-related gross microcracks (often
used in conjunction with microsectioning)
° Observation of grain boundaries in unetched samples
° Critical dimension measurements
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Sensitivity and Resolution
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| ° Lateral resolution for SEM: < 100Å |
| ° Lateral Resolution for EDX: 1 µm |
| ° Detection limits for EDX: 0.5 - 1% atomic |
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Instrumentation
° Hitachi 6600 Variable Pressure FE-SEM IXRF Systems Model 550i
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Silicon Drift Detector Elemental Mapping, SEI, BSE digital imaging
° JEOL 820i Scanning Electron Microscope with Kevex
light element
Quantum Energy Dispersive X-Ray Analyzer,
Digital Elemental
Imaging, Backscattered Electron Detection
° Cambridge Stereoscan 360 Scanning Electron Microscope
with 40kV LaB6
Emitter
° JEOL JSM-6060LV Variable Pressure Electron Microscope with Noran
Six-Sigma EDS
Advantages
° Depth of field is better than optical microscopy
or transmission
electron microscopy
° Fast, relatively inexpensive near-surface screening
method
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