Tungsten silicide composition analysis by Rutherford backscattering spectroscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy

Abstract

While Rutherford backscattering spectroscopy (RBS) is the accepted method for determining the composition of tungsten silicide films, the systems are expensive and not widely available. Furthermore, the depth resolution of RBS is of the order of 150 Å, which does not allow for the compositional analysis of thinner films. Also, chemical information is not available from RBS. These are critical issues as the geometries of ultralarge-scale integration devices become smaller. However, with special care applied to data acquisition and reduction, both Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) provide composition agreement with RBS. Additionally, AES and in particular XPS provide chemical information about thin films that is unavailable from RBS analysis. To demonstrate that AES and XPS provide composition analysis of thin films comparable to RBS, post-anneal tungsten silicide films deposited on silicon with both chemical and vapor deposition processes were analyzed by AES, XPS, and RBS. With care taken in data acquisition and reduction, silicon-to-tungsten ratios were comparable among the three techniques. Moreover, using AES and XPS, surface oxide thickness and interfacial layer composition can be determined.