The different available analysis techniques at Probion Analysis are described briefly below. For further details including figures and examples, please check Tutorials section.
SIMS (Secondary Ion Mass Spectrometry)
The surface of the sample is bombarded by a focused ions beam (O2+ or Cs+). The ions energy varies from 500eV to 15keV depending on the case. Typically the beam scans a square area 20µm to 500µm. A crater is thus formed due to the erosion of the surface by the sputtering. A small fraction of the ejected atoms are ionized: these are referred to as secondary ions. They are filtered according to their mass by a magnetic spectrometer and they are counted. The beam intensity is recorded as a function of erosion time.
La mesure des signaux en fonction du temps permet d’obtenir, en utilisant les étalons SIMS appropriés, des profils de concentration en fonction de la profondeur. Les étalons disponibles couvrent quasiment tous les besoins dans le domaine des semiconducteurs. Des spectres de masse (1-300uma) ou des images ioniques de la surface de l’échantillon peuvent aussi être obtenus.
XPS/ECSA (X-ray Photo-electron Spectrometry / Electron Spectrometry for Chemical Analysis)
The sample is irradiated by a monochromatic X-ray beam. Consequently, the core levels electrons are excited. A fraction of them are ejected from the sample: their energy distribution is measured using a spectrometer. The kinetic energy of these electrons is specific to the elements present in the sample.
A kinetic energy spectrum is measured. The peaks positions provide the electronic energy levels of sample atoms. Thus, the chemical elements can be identified and their concentrations can be calculated without the use of standards. The chemical bonds have also an influence on the spectrum: they generate some little shifts on the peaks energies. Some mathematical treatment provides the proportions of all types of bonds for each element.
ToF-SIMS (Time Of Flight Secondary Ion Mass Spectrometry)
In a static SIMS analysis, by using a pulsed primary beam, only a monolayer of the sample is attacked. Unlike a dynamic SIMS analysis, a static SIMS analysis preserve the molecular integrity of surface. Molecules are just desorbed or broken into several pieces. The secondary ions, constituted by initial molecules fragments, are detected by the time-of-flight spectrometer. Molecular ions as heavy as 10000amu can be detected thus providing information relating to the molecular structure of organic compounds.
Into the obtained mass spectra, the molecules which are present on sample surface are identified thanks to spectral signatures libraries.
RBS (Rutherford Backscattering Spectrometry)
The sample is bombarded by high energy He2+ ions (1 to 3MeV). These ions “probe” approximately a 1µm material thickness. Some of them are backscattered then detected. An energy spectrum of backscattered ions is measured using a solid state detector.
This technique provides quantitative information without the use of standards. The sensitivity of the technique is a function of Z2 and hence it is best suited for measurement of heavier elements in lighter matrices. It provides information relating to layer thicknesses, composition, implant dose and atom location when channeling.
ECVP (Electrochemical Capacitance Voltage Profiling)
The technique is dedicated to semiconductors doping analysis. The sample surface is immersed into a liquid electrolyte with several electrodes. The semiconductor-electrolyte junction has a behavior similar to that of a Schottky junction. Depending on electrical bias and optical lighting, the user can either chemically etch the sample, or measure its electrical capacitance with a reverse bias.
The technique is dedicated to the observation of structures such as integrated circuits at submicronic scales (10nm resolution). By FIB, an ultrathin lamella is cut out in the vertical structures of the sample. Then, this lamella is observed by TEM. The structures dimensions and some material compositions can be measured.
FIB-TEM (Focused Ion Beam - Transmission Electron Microscopy)
La technique est dédiée à l’observation de structures telles que des circuits intégrés à des échelles submicroniques (résolution 10nm). Par faisceau d’ions focalisés (FIB) une lamelle est découpée dans la structure verticale de l’échantillon. Cette lamelle est ensuite observée par TEM. Les dimensions des structures et certaines compositions de matériaux peuvent être mesurées.