Compositional depth profiling by auger electron spectroscopy

Abstract

Recent advances in Auger electron spectroscopy (AES) have been primarily in the areas of quantitative analysis and instrumentation. As instrumentation used in AES was recently extensively reviewed,^1,2 it will not be discussed here. This article considers the methods available to (1) convert measurements of Auger peak heights in the presence of sputtering to concen tration and (2) convert sputtering time to depth. Together, these methods constitute compositional or quantitative depth profiling. The lateral resolution of the depth profile is deter mined primarily by the diameter of the primary electron beam used in the analysis. Depth resolution, however, depends on the homogeneity of the sputter etching process, the homogeneity of the sample, and the escape depth of the emitted Auger electrons. Factors (other than ionelectron beam misalignment) which can cause inhomogeneity in the sputter etching process have been reviewed by Coburn and Kay,³ Coburn,⁴ Wehner,⁵ Benninghoven,⁶ and more recently by Shimizu⁷ and Hofmann.⁸ These factors include (1) the effect of angle of incidence on the sputtering process, (2) microtopographical changes (pitting, cone formation, faceting, etc.), (3) knock on, and (4) radiation-enhanced diffusion. The reader is referred to these articles and the references contained in them for further information.