Specific Process Knowledge/Characterization/SEM: Scanning Electron Microscopy

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Scanning electron microscopy in the cleanroom at DTU Nanolab

The number of electron microscopes at DTU Nanolab is large. The five SEMs in building 346 cover a wide range of needs both in the cleanroom and outside: From fast in-process verification of different process parameters such as etch rates, step coverages or lift-off quality to ultra high resolution images on any type of sample intended for publication.

  • The SEM Supra 1 is located in the basement outside the cleanroom. It is serving two purposes: Serving the users that have samples from outside the cleanroom and serving as training tool; all new SEM users with no/little SEM experience must be trained on this tool and gain basic knowledge (typically 10 hours of usage) here before being qualified for training on the SEMs in the cleanroom.
  • The SEM 2 and 3 are located in the cleanroom where they serve as general imaging tools for samples that have been fabricated in the cleanroom. Like SEM Supra 1, they are VP models from Carl Zeiss and will produce excellent images on any sample. The possibility of operating at higher chamber pressures in the VP mode makes imaging of bulk non-conducting samples possible. The SEM Supra 2 is also equipped with an airlock and an EDX detector.
  • The SEM Leo s a very reliable and rugged instrument that provides high quality images of most samples. It is exclusively dedicated to the users of the Raith E-beam lithography system so general imaging of user samples is not allowed.
  • The SEM Tabletop 1 is a tabletop SEM that is located in the basement outside the cleanroom. It has a limited resolution, but it is fast and easy to use, also for non-conducting samples. Training in the others SEMs is not required to use this SEM.

SEM Supra 1, 2 and 3 SEM Leo s all manufactured by Carl Zeiss and have the same graphical user interface and very identical electron optics. But there are there are small hardware and software differences, thus a training is needed for each SEM you want to use.

The SEM Tabletop 1 is manufactured by Hitachi.

Common challenges in scanning electron microscopy

Comparison of SEM's in building 346

Equipment SEM LEO SEM Supra 1 SEM Supra 2 SEM Supra 3 SEM Tabletop 1
Purpose Imaging and measurement of
  • Conducting samples
  • Semi-conducting samples
  • Thin (~ 5 µm <) layers of non-conducting materials such as polymers
  • Conducting samples
  • Semi-conducting samples
  • Thin (~ 5 µm <) layers of non-conducting materials such as polymers
  • Thick polymers, glass or quartz samples
  • Conducting samples
  • Semi-conducting samples
  • Thin (~ 5 µm <) layers of non-conducting materials such as polymers
  • Thick polymers, glass or quartz samples
  • Conducting samples
  • Semi-conducting samples
  • Thin (~ 5 µm <) layers of non-conducting materials such as polymers
  • Thick polymers, glass or quartz samples
  • Conducting samples
  • Semi-conducting samples
  • Thin (~ 5 µm <) layers of non-conducting materials such as polymers
  • Thick polymers, glass or quartz samples
Other purpose
  • E-beam lithography using Raith Elphy Quantum system
  • Surface material analysis using EDX
Instrument location
  • Cleanroom of DTU Nanolab in building 346
  • Basement of building 346
  • Cleanroom of DTU Nanolab in building 346
  • Cleanroom of DTU Nanolab in building 346
  • Basement of building 346
Performance Resolution The resolution of a SEM is strongly dependent on the type of sample and the skills of the operator. The highest resolution is probably only achieved on special samples
  • ~ 5 nm (limited by vibrations)
  • 1-2 nm (limited by vibrations)
  • 1-2 nm (limited by vibrations)
  • 1-2 nm (limited by vibrations)
  • ~25 nm (limited by instrument)
Instrument specifics Detectors
  • Secondary electron (Se2)
  • Inlens secondary electron (Inlens)
  • Backscatter electron (BSD)
  • Secondary electron (Se2)
  • Inlens secondary electron (Inlens)
  • 4 Quadrant Backscatter electron (QBSD)
  • Variable pressure secondary electron (VPSE)
  • Secondary electron (Se2)
  • Inlens secondary electron (Inlens)
  • 4 Quadrant Backscatter electron (QBSD)
  • Variable pressure secondary electron (VPSE)
  • Secondary electron (Se2)
  • Inlens secondary electron (Inlens)
  • High Definition four quadrant Angular Selective Backscattered electron detector (HDAsB)
  • Variable pressure secondary electron (VPSE)
  • Secondary electron (SE)
  • Backscatter electron (BSE)
Stage
  • X, Y: 125 × 100 mm
  • T: 0 to 90o
  • R: 360o
  • Z: 48 mm
  • X, Y: 130 × 130 mm
  • T: -4 to 70o
  • R: 360o
  • Z: 50 mm
  • X, Y: 150 × 150 mm
  • T: -10 to 70o
  • R: 360o
  • Z: 50 mm
  • X, Y: 130 × 130 mm
  • T: -4 to 70o
  • R: 360o
  • Z: 50 mm
  • X, Y: 35 mm
  • T: No tilt
  • R: No rotation
  • Z: 0 mm
Electron source FEG (Field Emission Gun) source
  • Thermionic tungsten filament
Operating pressures
  • Fixed at High vacuum (2 × 10-5mbar - 10-6mbar)
  • Fixed at High vacuum (2 × 10-4mbar - 10-6mbar)
  • Variable at Low vacuum (0.1 mbar-2 mbar)
  • Fixed at High vacuum (2 × 10-4mbar - 10-6mbar)
  • Variable at Low vacuum (0.1 mbar-2 mbar)
  • Fixed at High vacuum (2 × 10-4mbar - 10-6mbar)
  • Variable at Low vacuum (0.1 mbar-2 mbar)
  • Conductor vacuum mode: 5 Pa
  • Standard vacuum mode: 30 Pa
  • Charge-up reduction vacuum mode: 50 Pa
Options
  • Raith Elphy Quantum E-Beam Litography system
  • All software options available
  • Antivibration platform
  • Fjeld M-200 airlock taking up to 8" wafers
  • Oxford Instruments X-MaxN 50 mm2 SDD EDX detector and AZtec software package
  • High Definition four quadrant Angular Selective Backscattered electron detector (HDAsB)
Substrates Sample sizes
  • Wafers up to 6" (only full view up to 4")
  • Up to 6" wafer with full view
  • Up to 8" wafer with 6" view
  • Up to 6" wafer with full view
  • Up to 70 mm with full wiew
Allowed materials
  • Any standard cleanroom materials
  • Any standard cleanroom material and samples from the Laser Micromachining tool and the Polymer Injection Molding tool
  • Any standard cleanroom materials
  • Any standard cleanroom materials
  • Any standard cleanroom material and samples from the Laser Micromachining tool and the Polymer Injection Molding tool
  • Some biological samples (ask for permission)


Comparison of the SEMs at DTU Nanolab - building 307/314

Equipment Nova QFEG AFEG Helios
Purpose
  • Conductive samples in High Vac
  • Charge reduction in Low Vac
  • X Ray Analysis with EDS
  • Crystallographic analysis using EBSD and both On and Off axis TKD
  • In-situ experiments with Heating and Gas injection
  • Conductive samples in High Vac
  • Charge reduction in Low Vac
  • Environmental control using Peltier stage
  • Cryogenic sample fixing/stabilization using cryo stage
  • X Ray Analysis with EDS
  • Conductive samples in High Vac
  • Charge reduction in Low Vac
  • X Ray Analysis with EDS and WDS
  • Conductive samples in High Vac
  • Micro and Nano milling/fabrication using various gases and FIB
  • X Ray Analysis with EDS
  • Crystallographic analysis using EBSD and Off Axis TKD
Equipment position Building 314 Room 060 Building 314 Room 011 Building 314 Room 034 Building 314 Room 061
Resolution The resolution of a SEM is strongly dependent on sample type and the operator. Resolution quoted is using sputtered gold on carbon
  • High Vacuum operation in Mode II:
    • 1.0 nm at 15 kV (TLD detector and optimum working distance)
    • 1.8 nm at 1 kV (TLD detector and optimum working distance)
  • Low Vacuum operation in Mode II:
    • 1.5 nm at 10 kV (Helix detector and optimum working distance)
    • 1.8 nm at 3 kV (Helix detector and optimum working distance)
  • High vacuum
    • 0.8 nm at 30 kV (STEM)
    • 1.0 nm at 30 kV (SE)
    • 2.5 nm at 30 kV (BSE) - 3.0 nm at 1 kV (SE)
  • High vacuum with beam deceleration option
    • 3.0 nm at 1 kV (BD mode + BSE)
  • Low vacuum - 1.4 nm at 30 kV (SE)
    • 2.5 nm at 30 kV (BSE)
    • 3.0 nm at 3 kV (SE)
  • Extended vacuum mode (ESEM)
    • 1.4 nm at 30 kV (SE)
  • High vacuum
    • 0.8 nm at 30 kV (STEM)
    • 1.0 nm at 30 kV (SE)
    • 2.5 nm at 30 kV (BSE) - 3.0 nm at 1 kV (SE)
  • High vacuum with beam deceleration option
    • 3.0 nm at 1 kV (BD mode + BSE)
  • Low vacuum - 1.4 nm at 30 kV (SE)
    • 2.5 nm at 30 kV (BSE)
    • 3.0 nm at 3 kV (SE)
  • Electron Column Operation in Mode II
    • 0.8nm @15kV
    • 0.9nm @1kV
  • Ion Column
    • 4.5nm @ 30kV
Detectors
  • ETD/TLD Secondary Electrons
  • BSED Back Scatter Electrons
  • LVD/LFD Low Vac SE
  • Helix Low Vac SE
  • EDS X Ray by energy
  • EBSD Electron Back Scatter Diffraction
  • TKD Transmission Kikuchi Diffraction
  • STEM Scanning Transmission Electron Microscopy
  • GAD Low Vac BSED
  • ETD Secondary Electrons
  • BSED Back Scatter Electrons
  • LVD/LFD Low Vac SE
  • GSED ESEM SE
  • EDS X Ray by energy
  • STEM Scanning Transmission Electron Microscopy
  • ETD Secondary Electrons
  • BSED Back Scatter Electrons
  • LVD/LFD Low Vac SE
  • GSED ESEM SE
  • EDS X Ray by energy
  • STEM Scanning Transmission Electron Microscopy
  • ETD/TLD Secondary Electrons
  • ABS Annular BSED
  • EDS X Ray by energy
  • EBSD Electron Back Scatter Diffraction
  • CDEM Continuos Dinode Electron Multiplier
Stage specifications
  • X 150mm Piezo
  • Y 150mm Piezo
  • Z 10mm
  • R 360⁰ Piezo
  • T 70⁰
  • X 50mm
  • Y 50mm
  • Z 50mm
  • R 360⁰
  • T 70⁰ Manual
  • X 50mm
  • Y 50mm
  • Z 50mm
  • R 360⁰
  • T 70⁰ Manual
  • X 150mm Piezo
  • Y 150mm Piezo
  • Z 10mm
  • R 360⁰ Piezo
  • T 70⁰
Options B C D E
Max sample size Consult with DTU Nanolab staff as weight, dimensions, pumping capacity and technique all play a roll in the sample size


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