Grazing‐incidence x‐ray photoemission spectroscopy and the accuracy of thickness measurements of CMOS gate dielectrics

Grazing-incidence x-ray photoelectron spectroscopy (GIXPS) is a method that offers promise as a non-destructive technique to measure the thickness and chemical state of ultrathin gate dielectric films. This method utilizes the non-linear dependence of the photoelectron yield on the radiation incidence angle to characterize a given layer structure. The accuracy of the results also depends on the input parameters, such as photoemission cross-sections, indices of refraction and electron attenuation lengths within the incident x-ray energy range of application (1–2 keV). Uncertainties in these parameters have consequences not only for GIXPS but also for other techniques that rely on them for materials analysis. We present a study of the impact of uncertainty in the photoionization cross-sections and atomic scattering factors on the GIXPS measurement of film thickness and density. A test of the accuracy of the index of refraction is demonstrated by measurements of a native oxide layer on Si at incident energies below and above the Si K edge. We also discuss the effects of surface and interface roughness. Published in 2001 by John Wiley & Sons, Ltd.