Analysis Service for Industry and Research

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Different types of analysis: SIMS: Secondary ions mass spectrometry - TOF-SIMS: Time of flight SIMS - XPS: X-ray photoelectron spectrometry - RBS: Rutherford back scattering - ECVP: Electrochemical capacitance voltage profiling...

Different types of analysis: SIMS: Secondary ions mass spectrometry - TOF-SIMS: Time of flight SIMS - XPS: X-ray photoelectron spectrometry - RBS: Rutherford back scattering - ECVP: Electrochemical capacitance voltage profiling...

The techniques

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)

Experiment

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.

Result

The signals measurement versus time is converted into concentrations profiles versus depth with the use of appropriate SIMS standards. The available standards cover almost all needs in the field of semiconductors. Mass spectra (1-300amu) or ionic images of sample surface can also be obtained.

XPS/ECSA (X-ray Photo-electron Spectrometry / Electron Spectrometry for Chemical Analysis)

Experiment

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.

Result

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)

Experiment

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.

Result

Into the obtained mass spectra, the molecules which are present on sample surface are identified thanks to spectral signatures libraries.

RBS (Rutherford Backscattering Spectrometry)

Experiment

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.

Result

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)

Experiment

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.

Result

From capacitance measurements, one can calculate the doping level close to surface. By alternating etching and measuring phases, one analysis gives a doping profile versus depth.

FIB-TEM (Focused Ion Beam - Transmission Electron Microscopy)

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.