MODIFIED HIGH-RESOLUTION ELECTRON-ENERGY-LOSS SPECTRA APPLIED TO ANALYZE NANOMETER FEATURES IN ALSN SPUTTER FILMS

A modified technique is presented to record and evaluate electron ener gy loss spectra (EELS) which gives a lateral resolution for chemical a nalysis in the nanometre range. To achieve such a resolution, consider ations about the chromatic aberration and the behaviour of inelastical ly scattered electrons in magnetic lenses are necessary. The image-for ming system was approximated as consisting of four thin lenses for the computer modelling of ray paths. The results led to experimental cond itions for nanometre-scale resolution with EELS. The technique was app lied to analyse equidistant features first observed in oxygen-contamin ated AlSn sputter layers. Bright field transmission electron microscop e images of cross-sections show straight dark lines within individual Al crystals. The width of the lines is roughly 5 nm and their separati on varies from 50 to 100 nm. The comparison of spectra taken from the lines and from areas between revealed a marked increase in the tin and the oxygen content along the lines. This observation suggests a film growth in the presence of oxygen characterized by alternating regions of pure aluminium and of tin-oxide-enriched areas respectively. Tin ac ts as the oxygen-trapping species.