Characterization Method for Material Composition

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Characterization Method for Material Composition
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Outline

• X-ray Photoelectron Spectroscopy (XPS)
• Ultraviolet Photoelectron Spectroscopy (UPS)
• Auger electron spectroscopy (AES)
• Energy Dispersive X-ray Spectroscopy (EDX)
• Electron Energy Loss Spectroscopy (EELS)

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Photoelectron Spectroscopy
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X-ray Photoelectron Spectroscopy (XPS)

• 1967 Siegbahn Published comprehensive study on
  XPS
• 1969 Hewlett-Packard Produced the first
  commercial monochromatic XPS instrument
• 1981 Siegbahn received the Nobel Prize to
  acknowledge his extensive efforts to develop XPS
  into a useful analytical tool

Siegbahn
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Components of an XPS system

• Basic components of a monochromatic XPS system

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Application of XPS

• Elements that contaminate a surface
• Uniformity of elemental composition across the
  top surface (aka, line profiling or mapping)
• Uniformity of elemental composition as a function
  of ion beam etching (aka, depth profiling)

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Application of XPS

• Wide Scan Survey Spectrum for all elements

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Application of XPS

• High Resolution Spectrum for Si (2p) signal

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Ultraviolet Photoelectron Spectroscopy (UPS)
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Auger electron spectroscopy (AES)

• 1920s Auger effect Lise Meitner and Pierre Auger
• 1960s Auger Electron Spectroscopy

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Structure of AES
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Specification of AES Samples

• Size
• No larger than about 18 mm x 12 mm.Height
  should not exceed 12 mm.
• Conductivity
• Must be conductive or area of interest must
  be grounded properly. Insulating samples
  including thick insulating films (gt3000 Å) cannot
  be analyzed.
• Compatibility
• Must be compatible with high vacuum
  environment (lt1x10-9 Torr).

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Application of AES

• Survey scan
• Multiplex scan
• Mapping
• Depth profile

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Application of AES

• Particle identification
• Passive oxide film thickness
• Contact pad contamination on integrated circuits
• Quantifying light element impurities
• Mapping spatial distribution of surface
  constituents

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Application of AES

• AES survey spectrum for passivated stainless
  steel

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Application of AES

• Scanning Auger microscopy depth profile of
  passivated stainless steel

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Energy Dispersive X-ray Spectroscopy (EDX)

• A chemical microanalysis technique
• Performing in conjunction with a SEM
• Utilizing x-rays emitted from the sample during
  bombardment by the electron beam to characterize
  the elemental composition of the analyzed volume
• Features or phases as small as about 1µm can be
  analyzed

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Principle Structure of EDX
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Application of EDX

• Surface contamination analysis
• Corrosion evaluations
• Coating composition analysis
• Rapid material alloy identification
• Small component material analysis
• Phase identification and distribution

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Application of EDX

• Typical EDS spectrum

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Comparison of AES and EDX Analysis Volume
Capability

• AES is more sensitive than XPS.
• AES can be complement of XPS.

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Electron Energy Loss Spectroscopy (EELS)
A technique for studying atoms, molecules, or
solids in which a substance is bombarded with
monochromatic electrons, and the energies of
scattered electrons are measured to determine the
distribution of energy loss, which is known as
Electron Energy Loss Spectroscopy or EELS
Developed in 1940s by James Hillier
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Principle of EELS
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Principle Application of EELS

• The energy loss spectrum can be displayed and the
  loss profiles be used to identify elements in a
  specimen.

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Pro Con of EELS

• Advantages
• Elemental Analysis
• Elemental Imaging and Mapping
• Improved contrast without loss of resolution
• Thick specimen imaging
• Disadvantages
• Elemental analysis requires very thin specimens
  (10-20nm)

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Comparisons of EELS and EDS

• 1). EELS has higher spatial resolution than EDS.
• EDAX may be affected by backscattering
  electron,
• And fast secondary electron within the sample.
• 2). EELS has higher energy resolution than EDS.
  (around 1 eV)
• 3). EELS is better in detecting light element.
• 4). EELS contains information of electronic
  structure.
• 5). EDS is easy to operate and quick for a
  qualitative composition analysis.

However, EELS Spectra from thick specimens
(gt50nm) may be difficult to interpret because of
plural scattering. Interpretation of fine
structure sometimes requires sophisticated
calculations.