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Rutherford Backscattering Spectrometry (RBS)

Rutherford Backscattering Spectrometry (RBS) is an ion scattering technique used for compositional thin film analysis. RBS is unique in that it allows quantification without the use of reference standards. During an RBS analysis, high-energy (MeV) He2+ ions (i.e. alpha particles) are directed onto the sample and the energy distribution and yield of the backscattered He2+ ions at a given angle is measured. Since the backscattering cross section for each element is known, it is possible to obtain a quantitative compositional depth profile from the RBS spectrum obtained, for films that are less than 1μm thick.

In addition to elemental composition, RBS can be used to obtain information on the crystalline quality of single crystal samples.  This technique, called “channeling”, can probe the degree of damage in a crystal, or determine the amount of substitutional or interstitial species in a lattice.

EAG has world-class experience in analyzing thin films using RBS, with both pelletron and tandetron instrumentation. EAG’s experience in the analysis of all types of  thin films (oxides, nitrides, silicides, high and low-K dielectrics, metal films, compound semiconductors and dopants) enables fast turnaround times, accurate data, and high quality person-to-person service.

Ideal Uses
  • Thin film composition/thickness
  • Determine areal concentrations (atoms/cm2)
  • Determine film density (when thickness is known)
Technical Specifications

Signal Detected: Backscattered He atoms
Elements Detected: B-U
Detection Limits: 0.001-10at%
Depth Resolution: 100-200Å
Imaging/Mapping: No
Lateral Resolution/Probe Size: >=2mm

Strengths
  • Non-destructive compositional analysis
  • Quantitative without standards
  • Whole wafer analysis (up to300mm) as well as irregular and large samples
  • Conductor and insulator analysis
  • Hydrogen measurements (in HFS mode)
  • Low-Z element sensitivity (in NRA mode)
Limitations
  • Large analysis area (~2mm)
  • Useful information limited to top ~1μm of samples