Variations of X-ray spectrum in total reflection X-ray fluorescence (TXRF) analysis with respect to Si wafer crystal orientation for different incident angles

Abstract

This work studies the W-L-beta, Si-K-alpha and spurious radiations, which occur in the total reflection X-ray fluorescence (TXRF) analysis technique, Measurements at different azimuth angles were studied with respect to; the wafer orientation under different incident glancing angles of the X-ray beam on the surface of a bare Si-wafer, an oxide film, and an amorphous silicon film. It was found that both the W-LB radiation and the spurious radiation signals have a four fold periodic;variation with respect to the wafer orientation while the Si-K-alpha radiation signal does not have such a variation. For the oxide wafers, this periodic variation for the W-L-beta radiation and the spurious radiation signals becomes less and eventually disappears as the thickness of the oxide increases to 42 nm. For the amorphous silicon wafer, the above periodic variation phenomenon does not exist. This reveals that the W-L-beta and the:spurious radiation signals are mainly due to the interaction of incident X-ray evanescent radiation with the silicon crystal lattice. To reduce spurious signals in the TXRF analysis, a measurement at azimuth angle along the [100] directions of 45, 135, 225 or 315 degrees to the oxide-covered surface is suggested.