Issues on thickness measurements of nm HfO2 film by X-ray photoelectron spectroscopy

In the mutual calibration for determination of ultrathin oxide film thickness, the thickness measured by X-rayphotoelectron spectroscopy (XPS) has been known to be representative offset traceable. The offset traceability of XPS has been proved in the Consultative Committee for Amount of Substance (CCQM) pilot study P-190. For the analysis of nm HfO2 film thickness by XPS, a general equation is used involving the relative peak intensity (Ro) of pure HfO2 film and the substrate. The difference in the surface polarity of HfO2 film and substrate induces different amount of surface carbon contamination, which leads to the error in Ro value. In the plot of XPS and reference thickness of HfO2 films, the correction for the carbon contamination results in the offset value of -0.014 nm, while a larger offset value of -0.219 nm was measured without the carbon correction. Furthermore, different from the thickness measurement of SiO2 film, the reference geometry configuration is not important factor for the thickness measurement of ultrathin amorphous HfO2 films.