Application of Cr Kα X-ray photoelectron spectroscopy system to overlayer thickness determination

A laboratory hard X-ray photoelectron spectroscopy (HXPS) system at 5.4-keV excitation energy was used to measure the angle dependence of a silicon oxide overlayer on a Si(0 0 1) substrate with overlayer thickness ranging from 4 to 25 nm. The thickness values of the SiO2 overlayers were determined by utilizing a focused monochromatized Cr K alpha source and a high-energy hemispherical analyzer with an angle-resolved wide acceptance angle objective lens. The modulation of the photoemission intensity due to photoelectron diffraction, which deteriorates high-precision thickness determination, was suppressed significantly by continuous sample rotation around the sample's normal during the measurements. The resultant thickness values very well agree with those determined by ellipsometry in the same sample set. To demonstrate merits of the large information depth measurements, profiling of a wedged SiO2 layer buried in a gate stack model structure with Ir (8 nm) and HfO2 (2 nm) overlayers was performed. Copyright (C) 2011 John Wiley & Sons, Ltd.