ESTIMATION OF FILM THICKNESS FROM THE BACKGROUND SIGNAL IN X-RAY PHOTOEMISSION SPECTROSCOPY

A nondestructive estimation of the thickness of a uniform overlayer has been investigated using x-ray photoemission spectroscopy (XPS), which is an application of Tougaard's formalism. It has been shown that it is possible to estimate the thickness of an overlayer existing on a semi-infinite underlayer, by measuring the ratios of the peak area to the background signal on the high binding energy side of a photoelectron peak produced by an element existing in an underlayer before and after removing the overlayer. Especially when the inelastic mean free path of a photoelectron in an overlayer and an underlayer can be approximated equal, the relation between those ratios and the overlayer thickness is expressed in a very simple mathematical form. This method has been applied to various thickness of a-Si:H overlayers on SiNxformed by plasma chemical vapor deposition (CVD) method. A good linear correlation has been obtained between the thickness estimated by this method and that estimated from the deposition time, and thus the validity of this method has been shown. © 1990, American Vacuum Society. All rights reserved.