Thickness measurement of nm hfo2 films

A pilot study for the thickness measurement of HfO2 films was performed by Surface Analysis Working Group (SAWG) of Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study is to ensure the equivalency in the measurement capability of national metrology institutes for the thicknesses measurement of HfO2 films. In this pilot study, the thicknesses of six HfO2 films with the nominal thickness range from 1 nm to 4 nm were measured byX-ray Photoelectron Spectroscopy (XPS), X-ray Reflectometry (XRR), X-ray Fluorescence Analysis (XRF), Transmission Electron Spectroscopy (TEM), Spectroscopic Ellipsometry (SE) and Rutherford Backscattering Spectrometry (RBS). The reference thicknesses were determined by mutual calibration of a zero offset method (Medium Energy Ion Scattering Spectroscopy (MEIS) of KRISS) and a length unit traceable method (the average thicknesses of three XRR data except the thinnest film). These reference thicknesses are traceable to length unit because they are based on the traceability of XRR. It should be noted that the amount of substance of HfO2 expressed in the usual units of mass per unit area was obtained directly by RBS and indirectly through a further analysis (by NIST) of the XRR data, demonstrating that these films were markedly less dense than bulk. For the thickness measurement by XPS, the effective attenuation length of Hf 4f electrons has been determined. In the cases of XRR and TEM, the offset values can be determined from the linear fitting between the reference thicknesses and the individual data by XRR and TEM. The amount of substance of HfO2, expressed as thickness of HfO2 films (in both linear and areal density units), was found to be a good subject for a CCQM key comparison.