Intercomparison of silicon dioxide thickness measurements made by multiple techniques: The route to accuracy

A pilot project has been launched under the auspices of the Consultative Committee for Amount of Substance to evaluate the quantification for SiO2 on (100) and (111) Si in the thickness range 1.5–8 nm. Wafers and methodologies have been carefully prepared. Forty-five sets of measurements have been made in different laboratories using eight methods: medium energy ion scattering spectrometry (MEIS), nuclear reaction analysis (NRA), Rutherford backscattering spectrometry (RBS), elastic backscattering spectrometry (EBS), x-ray photoelectron spectroscopy (XPS), ellipsometry, grazing incidence x-ray reflectometry (GIXRR), neutron reflectometry (NR), and transmission electron microscopy. The results have been assessed, against the National Physical Laboratory (NPL) XPS data, using d(respondee)=md(NPL)+c. All show excellent linearity. The main sets correlate with the NPL data with average root-mean-square scatters of 0.13 nm with half being <0.1 nm. Each set allows the relative scaling constant, m, and the zero thickness offset, c to be determined. Each method has 0