Secondary Ion Mass Spectrometry

Structural & Morphology Characterization (Electron and ion beam technologies)

SIMS uses a focused, energetic primary ion beam to bombard the surface of the sample of interest. Sample atoms are sputtered and those that are ionized (secondary ions) are accelerated towards a mass spectrometer where they are mass separated before being detected. Either positive or negative secondary ions are detected. The use of a reactive primary ion beam can increase the secondary ion yield. Oxygen is used to increase positive secondary ion yield and cesium is used to increase negative secondary ion yield. There are three main types of spectrometer that are used to mass-separate the secondary ions, magnetic sector, time-of-flight, and quadrupole spectrometers. Magnetic SIMS provides the best detection limits whilst time-of-flight (TOF)-SIMS provides the highest surface sensitivity when used with a pulsed analysis gun. SIMS can provide surface mass spectra, images with lateral resolution in the 0.1 to 10 µm range and depth profiles with depth resolution in the 1 to 10 nm range. SIMS can be quantitative when reference samples are used and can achieve ppm or even ppb sensitivity. Profile depths can range from a few tens of nanometers to several tens of microns and any vacuum compatible sample can be analyzed. Some samples may require specific sample preparation (notably for biological samples) and analysis conditions. For example organic samples may be damaged by mono-atomic ion beams and the use of cluster ion beams (such as Argon clusters) can reduce this damage, thus enabling large molecular ions, characteristic of the sample to be detected.

          provided at NFFA-Europe laboratories by:
          provided by:
Element profiling, surface contamination, molecular depth profiling, 2-D and 3-D imaging, FIB-ToF SIMS imaging, FIB-ToF-SIMS tomography
Bi pulsed sources, Cs, Xe, Argon cluster and O source for abrasion Ga source for FIB sectioning Electron gun for charge compensation
Argon cluster from 2 kV to 20 kV, cluster size from 500 to 5000 atoms per projectile Cs, Xe, O, Ar monoatomic ion sputter source can operate from 250 eV to 2000 eV Bi analysis source can operate from 15kV to 30kV Ga FIB source operates at 30 kV
ION TOF Reflection TOF mass spectrometer with enhanced data rate technology to avoid detector saturation for intense signals (e.g. 28Si or Cs+) Mass resolution up to 10000 m/dm.
Depth resolution: >1 nm Spatial resolution: >40 nm Mass resolution < 10000 m/dm
Tilt angle +/- 5°, full rotation and access to all areas of a 100 mm wafer Imaging can be performed on large areas up to 100 mm in diameter by rastering the stage
Samples can be from a few mm up to 100 mm wafers Any vacuum compatible sample can be analysed Sample thickness should be less than 2 cm Samples can be heated up to 400°C and cooled down to -130°C
Main vacuum pressure is in the 1E-9 to 1e-10 mbar range
It is possible to transfer samples under UHV or N2 to AFM, XPS, and Auger tools
Most of our projects are related to polymers and organic compounds, together with a focus on biological applications, but also semiconductors and other scientific fields are included in our expertise. SIMS is – complementary to XPS – a surface analysis technique providing elemental and molecular information at high lateral resolution. A focused high energy ion beam is used to bombard the surface of the sample releasing characteristic fragments of the material to be analyzed. Secondary ions are mass separated and counted resulting in a mass spectrum of the sample (information depth approx. 2 nm). The lateral distribution of chemical functionalities can be obtained by rastering the primary beam and the sample itself. ToF-SIMS is ideally suited for the analysis of polymers, or thiol self-assembled monolayers, as well as surfaces from technical applications and environmental studies. Depth profiling and 3D imaging is performed by applying a sputter ion source eroding the sample with cesium, oxygen, or argon cluster ions. Charge compensation on insulating samples is facilitated by an electron flood gun.
Primary ion source: Liquid metal ion source, providing an Bi+ / Bi3+ pulsed beam at 25 keV Sputter ion sources: Oxygen and Cesium, Argon cluster ion source (for depth profiling in organics)
Time-of-flight mass analyzer
On suitable samples down to 200 nm
Best size 1x1cm approx. vacuum stable. Details available on request.
Typical secondary ion mass range 1-500 amu
Mass resolution up to 8000 m/Dm
IONTOF data files