Reference-Free Total Reflection X-ray Fluorescence Analysis of Semiconductor Surfaces with Synchrotron Radiation

Abstract

Total reflection X-ray fluorescence (TXRF) analysis is a well-established method to monitor lowest level contamination on semiconductor surfaces. Even light elements on a wafer surface can be excited effectively when using high-flux synchrotron radiation in the soft X-ray range. To meet current industrial requirements in nondestructive semiconductor analysis, the Physikalisch-Technische Bundesanstalt (PTB) operates dedicated instrumentation for analyzing light element contamination on wafer pieces as well as on 200- and 300-mm silicon wafer surfaces. This instrumentation is also suited for grazing incidence X-ray fluorescence analysis and conventional energy-dispersive X-ray fluorescence analysis of buried and surface nanolayered structures, respectively. The most prominent features are a high-vacuum load-lock combined with an equipment front end module and a UHV irradiation chamber with an electrostatic chuck mounted on an eight-axis manipulator. Here, the entire surface of a 200- or a 300-mm wafer can be scanned by monochromatized radiation provided by the plane grating monochromator beamline for undulator radiation in the PTB laboratory at the electron storage ring BESSY II. This beamline provides high spectral purity and high photon flux in the range of 0.078-1.86 keV. In addition, absolutely calibrated photodiodes and Si(Li) detectors are used to monitor the exciting radiant power respectively the fluorescence radiation. Furthermore, the footprint of the excitation radiation at the wafer surface is well-known due to beam profile recordings by a CCD during special operation conditions at BESSY II that allow for drastically reduced electron beam currents. Thus, all the requirements of completely reference-free quantitation of TXRF analysis are fulfilled and are to be presented in the present work. The perspectives to arrange for reference-free quantitation using X-ray tube-based, table-top TXRF analysis are also addressed.

Atomic Layer Deposition of High-κ Dielectrics on Sulphur-Passivated Germanium

“…Employing well-characterized synchrotron radiation and calibrated detectors, the TXRF measurements allow for reference-free quantification of the amount of S. 14 The monochromatized radiation hits the vertically mounted samples under a grazing incidence angle below the angle of external total reflection. The fluorescence radiation emitted by the samples was recorded by an energy dispersive Silicon Drift Detector (SDD).…”

Comprehensive Comparison of Various Techniques for the Analysis of Elemental Distributions in Thin Films: Additional Techniques

“…This stepwise approach enables a numerically stable fit for the total error square χ 2 of the calculated and measured intensities. The total, relative uncertainties range from 0.06 to 0.15, which is related to the uncertainties of the atomic fundamental, the experimental, and the instrumental parameters, with main contributions from atomic fundamental parameters, such as fluorescence yields (ranging from 0.03 to 0.1), photoionization cross sections, and transition probabilities (Beckhoff et al, 2007;Zschornack, 2007), as well as from the uncertainties of the least-square fit. For the elemental concentrations, total errors sum up to about 1-2 at.%, where we take the upper limit for error bars in the viewgraph of Fig.…”

A new generation of x-ray spectrometry UHV instruments at the SR facilities BESSY II, ELETTRA and SOLEIL

“…To fully explore these analytical capabilities, a flexible UHV instrument is required, e.g. for varying the angle of incidence of the exciting radiation ranging from total reflection-(TXRF) 8 , grazing incidence-(GI) to conventional XRF. While the sensitivity increases with decreasing angle of incidence, the quantification reliability meets challenges regarding the knowledge of the X-ray standing wave (XSW) field and the solid angle of detection.…”