Accuracy of film thickness determination in electron probe microanalysis

Abstract

The thickness of copper films (100-450 nm) on silicon substrates was determined by electron probe microanalysis (EPMA) applying ~b(pz) procedures of Pouchou and Pichoir. Film thickness was calculated from experimental k-ratios analyzed with electron energies between 6 and 30 keV using commercial software (LAYERF distributed by CAMECA). The influence of the incident electron energy and X-ray line chosen for analysis on the results was investigated. Accuracy of film thickness determination was evaluated by comparison with Rutherford backscattering spectroscopy (RBS) and secondary ion mass spectrometry (SIMS). The difference between layer thicknesses determined with EPMA and RBS is in general less than 2%, if EPMA measurements are performed with various electron energies. Layer thicknesses determined with Cu-Le are mostly closer to values obtained by RBS than those derived from Cu-K~ radiation. Preliminary SIMS measurements yielded inconsistent results and, thus, cannot be used in this case to determine the layer thickness of Cu films on Si accurately.

Measuring the Thickness of Metal Coatings: A Review of the Methods

“…The calibration curve can be obtained using standards of known thickness [157] or Monte Carlo simulations [20,21]. In terms of the quantification method, the quantity used in the calibration curves, multiple alternatives were evaluated: the K-ratio [153,[158][159][160], which is the ratio between the intensity in the sample and the intensity in a standard with known composition, commonly used in quantification; the ratio of intensities [161]; and the atomic ratio [157], obtained performing the ZAF correction algorithm on the K-ratios. Both the absolute thickness [162,163] as well the mass thickness [164][165][166][167] were taken into consideration for the quantification.…”

Measuring the Thickness of Metal Films: A Selection Guide to the Most Suitable Technique

“…The calibration curve can be obtained using standards of known thickness [131] or Monte Carlo simulations [19,20]. In terms of the quantification method, the quantity used in the calibration curves, multiple alternatives were evaluated: the K-ratio [127,[132][133][134], which is the ratio between the intensity in the sample and the intensity in a standard with known composition, commonly used in que quantification analysis; the ratio of intensities [135], and the atomic ratio [131], obtained performing the ZAF correction algorithm on the K-ratios. Both the absolute thickness [136,137] as well as the mass thickness [138][139][140][141] were taken into consideration for the quantification.…”

Measuring Non-Destructively the Total Indium Content and Its Lateral Distribution in Very Thin Single Layers or Quantum Dots Deposited onto Gallium Arsenide Substrates Using Energy-Dispersive X-ray Spectroscopy in a Scanning Electron Microscope

“…The penetration depth of electrons into the sample also influences the depth in which the majority of X-rays are produced. This has been traditionally used in the past to adjust the depth sensitivity of SEM-EDXS and to measure the thicknesses of surface coatings, however, mainly for relatively thick layers in the range >0.05 µm, up to several µm [21][22][23].…”