Photoelectron bremsstrahlung spectrum in synchrotron radiation excited total reflection x-ray fluorescence analysis of silicon wafers

Abstract

When synchrotron radiation is used as an excitation source, the total reflection x-ray fluorescence analysis of surface contamination on silicon wafer has an extremely low background intensity that determines the minimum detection limit. In this article, the background spectrum originating from the photoelectron bremsstrahlung is calculated using the Monte Carlo method. The doubly differential electron bremsstrahlung cross sections obtained from the Born approximation modified by the Elwert factor and with the use of the form factor approach for screening are used instead of empirical formulas. In addition to the bremsstrahlung spectrum produced from the silicon wafer, the bremsstrahlung intensity that photoelectrons, which escape from the silicon wafer, produce in the filter attached to the detector is also calculated in accordance with the usual synchrotron radiation excited total reflection x-ray fluorescence experimental conditions. The calculated photoelectron bremsstrahlung spectra are compared with experimental results and the conditions for a lower minimum detection limit are discussed. (C) 1999 American Institute of Physics. [S0021-8979(99)01814-9].