DEPTH PROFILING USING TOTAL-REFLECTION X-RAY-FLUORESCENCE SPECTROMETRY ALONE AND IN COMBINATION WITH ION-BEAM SPUTTERING

The capability of total reflection X-ray fluorescence spectrometry (TX RF) for depth profiling is examined by means of selected examples incl uding organometallic layers, an implantation profile of arsenic in sil icon and a layered nickel/cobalt structure. For structures without den sity differences that are deeper than 20 nm or so, and also for buried layers and for the examination of sharp interfaces, which require the highest resolution, two different combinations of ion beam sputtering with TXRF have been employed. A microsectioning technique was investi gated in which samples were etched to a bevel shape and subsequently s canned by TXRF. A depth resolution of 2.5 nm was obtained. Alternative ly, the so called ''transfer technique'' was investigated. This involv es surface atoms being sputtered by an ion beam and immediately deposi ted on a silicon wafer rotated behind a slit which is moved in step wi th the sputter progress. Subsequently, the wafer is scanned by TXRF. U sing this technique, the width of a coherent Ti/Al interface within a layered structure was measured to be 1.4 nm. The depth resolutions of the ''microsectioning'' and the ''transfer'' techniques are compared w ith data from RES, XPS, SIMS and SNMS. (C) 1997 Elsevier Science B.V.