Embed Size (px)
Citation preview
Scanning Electron Microscope & Surface Analysis
Wageningen EM Centre
Marcel Giesbers
Scanning Electron Microscope & Surface Analysis
2
SEM vs Light Microscope and Transmission EM
Secondary Electron ImagingBackscatter Imaging
Energy Dispersive X-ray Spectrometry (EDX / EDS)
Layer thickness determination By EDXBy cross section
Summary
Light Microscope & Transmission Electron Microscope
3
Transmission Electron Microscope (TEM)Light microscope
The Scanning Electron Microscope (SEM)
4
Information from the electron specimen interactions
5
6
Different signals from different regions in the specimen.
Sampling volume volume from which a particular signal (e.g. X-rays) originates
Interaction volume 15kV electrons travel ~1 μ into sample
Regular SEM imaging of secondary electrons
7
The SEM image is a 2D intensity map
8
The scanning on the computer screen is synchronized with the electron-probe scan. Brightness variations, depends on the number of the secondary electrons collected, forms the SEM image
The SEM image is a 2D intensity map
Sample surface
Beam scans the sample
Backscatter imaging
9
The incoming electrons are “reflected” back out of the sample
Backscatter imaging
10
In Backscatter imaging, the signal is dependent on the atomic number.
Energy Dispersive X-ray Spectrometry (EDX or EDS)
11
12Transistor
X-ray spectrum is acquiredElements are identified and labelled.The higher the peak, the higher the concentration of that element
13
14
15
16
EDX analysis in SEM output
17
Element Line Type
Wt% Wt% Sigma
C K series 60.72 0.28
O K series 25.22 0.25
P K series 0.56 0.04
Ca K series 0.65 0.05
Fe K series 8.72 0.18
W M series 4.13 0.16
Total: 100.00
Quantitative analysisSensitivities to 0.1 wt. %Depending on matrix and composition
Qualitative elemental analysis
EDX analysis in SEM
18
Linescans Pointspectra
Elemental composition along a line
Elemental maps
Thin film Thickness Measurements by SEM
19
Question:Silicon Nitride layer on SiliconHow thick is this layer?
Methods in SEM
1) EDX analysis
2) Cross section image of the sample
Thin film Thickness Measurements by EDX
20
EDX Can also be used to calculate the composition and thickness of the individual layers beneath the surface.
X-rays
Bulk material
X-rays
Bulk material
overlayer
Overlayer thickness can be calculated from the attenuation of the X-rays.
X-ray spectrum
Layer thickness determination by EDX
21
Define a model in the software->composition, density and layers
Choose analysis conditions
Acquire spectrum
Siliconnitride layer on silicon
Software fits the datacalculates layers
Layer thickness and composition characterization using EDX
22
Calculating the composition and thickness of the individual layers beneath the surface• non-destructive• high-resolution
Characterises features down to 200 nm wide• Suitable for metallic layers
Usefull for • coatings• thin film deposition processes• oxide layer formation
Layer thickness determination by cross section imaging
23
Cross Section Polisher
Shell particles cross-section of solar cell
Silicon nitride layer on Silicon
24
Layer thickness by EDX:
EDX Imaging the Cross Section
Layer thickness by EDX95.0nm
Layer thickness by cross section96.5nm
Silicon oxide layer
25
Layer thickness by EDX37.5nm
EDX Imaging the Cross Section
Layer thickness by cross section36.5nm
Summary
26
• SEM uses a high energy beam of electrons to create images of a surface. Usually secondary electrons are used for this imaging.
SEM is capable of more:• Backscatter imaging can be used to differentiate contrasts in a material
comprising of different chemical compositions.
• EDS in SEM (X-rays) can be used to identify the composing elements of materials surface. EDX does not reveal chemical bonding information.
• qualitative & quantitative elemental analysis• elemental mapping, linescans, point spectra• works on conductive and non-conductive samples.
• EDS can be used for layer thickness characterization.• non-destructive analysis of layers• high-resolution.• thickness range 1-2000nm
