Measurement of the thickness of thin layers by proton- induced X-ray emission

The thickness of copper layers (5–200 nm) was measured from the Cu L X-ray excitation of the thin layers by bombardment with protons of energy 280 keV. The method was based on a comparison of the expected X-ray yield (calculated from thick target yield measurements) with the measured yield at the thin layer. The absolute accuracy achieved was better than ten per cent. The thickness distribution of the extended evaporated layers shows a cos 6( r h ) dependence. The results demonstrate that it is difficult to produce layers of known thickness controlled only by the quartz oscillation method because the steam direction from a boat-like evaporation source is uncertain.