Beyond conventional secondary electron imaging using spectromicroscopy and its applications in dopant profiling

Abstract

Despite decades of research, the technique of measuring dopant concentration by the scanning electron microscope (SEM) has so far been limited to probing idealized test pn junction specimens, where only step dopant concentrations have been quantified. This article presents experimental results to demonstrate that the key to making this method reliable is to use a high signal-to-noise secondary electron (SE) energy spectrometer attachment and how quantifying small changes in spectral signal shape overcomes longstanding problems, such as making dependable measurements in the presence of a silicon native oxide layer. Dopant profiling of a solar cell precursor device were also found to be in good agreement with other conventional dopant profiling methods. In addition, new possibilities have been discovered, such as in situ measurement of native oxide thickness and the mapping of space-charge density. These results point towards SE energy spectroscopy having the potential to become a new analytical technique for SEMs.