Accurate Thickness Determination of Both Thin SiO2 on Si and Thin Si on SiO2 by Angle-Resolved X-Ray Photoelectron Spectroscopy

Abstract

Thicknesses of both ultrathin silicon oxide on silicon substrate and ultrathin silicon on silicon oxide are accurately determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The effective attenuation lengths of Si 2p photoelectrons in silicon oxide, λO, and silicon substrate, λS, are accurately determined by considering the photoelectron yields in both materials, which were obtained experimentally from the damping of intensities of the plasmon-loss peaks therein. Photoelectron yields for silicon oxide and silicon substrate are YO = 0.91 and YS = 0.74, respectively, and consequently the relationship between λO and λS is λO=1.4 λS. The value of λS is accurately determined from the silicon-on-insulator (SOI) sample with a thickness of 5 nm to be λS = 2.3 nm and the value of λO is subsequently determined to be 3.2 nm. Finally, the value of λO is confirmed by comparing the oxide thicknesses of SiO2 on Si(100) systems determined by AR-XPS with those determined by ellipsometry.